29 August 2013 Last updated at 08:05 ET 
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The BBC's Jeremy Bowen in Damascus: "People are going about their daily business but there is a lot of anxiety"
UN Secretary General Ban Ki-Moon says he will receive a report on Saturday from weapons inspectors investigating an apparent Syrian chemical attack.
Hundreds are reported to have died in the attack near Damascus last week.
US President Barack Obama has said he has not yet decided on a plan for retaliatory action against Syria.
Other nations are also considering the next move. The UK wants a UN Security Council resolution to take "all necessary measures" to help civilians.
A UK intelligence committee said in a statement that "if action in the UN Security Council is blocked, the UK would still be permitted, under the doctrine of humanitarian intervention, to take exceptional measures including targeted military intervention, in order to alleviate the overwhelming humanitarian suffering in Syria".
Syrian President Bashar al-Assad said his country would defend itself against any aggression.
The British parliament is voting later on Thursday on whether to back the principle of military intervention, but the leader of the opposition Labour Party has said MPs should not have to decide on what he called an "artificial timetable".
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At the scene
Damascus seems quieter than on trips I made here earlier this year, though there's still plenty of traffic in the centre. Its people are awaiting decisions that are being taken elsewhere.
Army roadblocks stop traffic every few miles down the highway in from the Lebanese border, as they have since the war started.
News agencies, quoting residents and some opponents of the Assad regime, have reported that some heavy weaponry has been moved out of bases and staff have partially vacated some headquarters.
It is logical for the Syrian army to have some sort of plan to protect itself from any attack, especially since the progress toward launching a military strike has been discussed so openly by Western powers.
The countries surrounding Syria are bracing themselves for a new crisis. In Beirut, the man who helped me with my bags said the West would do whatever it wanted.
"But please, don't bomb anywhere near Lebanon. We fear another big war."
The Speaker of the Syrian parliament has written to his counterpart in London inviting a British parliamentary delegation to visit Damascus as soon as possible.
French President Francois Hollande has also yet to decide about a military intervention. But on Thursday, after meeting Ahmed Jarba, the head of the opposition Syrian National Coalition, Mr Hollande said a political solution would only be possible if "the international community can put a temporary stop to this escalation in violence".
Meanwhile, the Chinese state newspaper China Daily has warned there are no excuses for air strikes on Syria - with an editorial accusing Western powers of acting as judge, jury and executioner before the UN has completed its investigation.
Russia, President al-Assad's main international ally, also says it opposes any foreign military intervention in Syria.
Russia is sending an anti-submarine ship and a missile cruiser to the eastern Mediterranean.
The ships are being sent to strengthen the navy's presence in the area because of the "well-known situation" there, the Russian news agency Interfax has said.
But another news agency, RIA Novosti, quotes a senior naval command spokesman as saying that this is just a planned rotation, unconnected with Syria.
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Ban Ki-moon: "Inspectors will report to me as soon as they come out"
Britain says it is sending six Typhoon fighter jets to Cyprus, in what it says is a measure to protect British bases there.
'Inventing excuses' The UN weapons inspectors are now in their third day of on-site investigations at the sites of an alleged chemical attack near Damascus.
The UN secretary general has appealed for the team to be "given time to do its job".
Syria denies using chemical weapons and blames opposition fighters for the attack on 21 August, which reportedly killed hundreds of people near Damascus.
It accused the West of "inventing" excuses to launch a strike.
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President Obama: ''I have no interest in any kind of open-ended conflict in Syria''
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Obama is said to have wanted to act before leaving the US for a foreign trip next Tuesday - If he still wants to stick to that timetable, Britain will no longer be with him"
End Quote In a sign of growing fears about an impending attack among Syrians, the Associated Press quoted Lebanese officials as saying at least 6,000 Syrians crossed into Lebanon in a 24-hour period through the main Masnaa crossing - compared to a normal daily tally of between 500 and 1,000 refugees.
"Isn't it enough, all the violence and fighting that we already have in the country, now America wants to bomb us, too?" one 45-year-old woman, entering Lebanon with her five children, told AP.
In Damascus, senior military commanders are reportedly staying away from buildings thought likely to be targeted. You "could hear a pin drop" at one of them, a local resident said.
But state television is portraying citizens going about their normal lives, seemingly unperturbed by the prospect of possible military strikes.
'Consequences' President Obama told the US Public Broadcasting Service (PBS) that the US had "not yet made a decision" on whether to take retaliatory action against Syria, but "the international norm against the use of chemical weapons needs to be kept in place, and hardly anyone disputes that chemical weapons were used in a large scale in Syria against civilian populations".
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Military intervention is morally justified"
End Quote Anthony Luder Safed, IsraelContinue reading the main story
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Intervening now in Syria would be a terrible mistake"
End Quote Demetrios Nicolaides Limassol, Cyprus "We've looked at all the evidence, and we don't believe the opposition possessed chemical weapons of that sort," he said.
He added he had concluded that the Syrian government carried out the chemical weapons attack.
"There need to be international consequences, so we are consulting with our allies," he said.
Critics have questioned what purpose a limited strike on Syria could serve, but Mr Obama said it would send the government of Bashar al-Assad "a pretty strong signal that it better not [use chemical weapons] again".
The BBC's David Willis in Washington says this is the most unequivocal sign that Mr Obama has given that he believes the Syrian government is guilty of deploying chemical weapons.
Despite that, our correspondent says, Mr Obama looked cautious and spoke in a measured way, and he was clearly concerned about getting Congress on board as well as the American public.
Opinion polls until now have shown very little interest among the US public in getting involved in the Syrian conflict.
In an open letter to the president, US House of Representatives Speaker John Boehner demanded he explain "the intended effect of military strikes", and how he would prevent the intervention escalating, if he wanted to win public and congressional backing for action.
US officials are expected to give senior members of Congress a classified briefing on the evidence that the Syrian government carried out the alleged chemical attack on Thursday.
The US has said it will not take action alone - but one of its primary allies, the UK, has agreed to wait until UN inspectors report back before taking a final parliamentary vote on potential action.
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The BBC's John Simpson explains the cases for and against intervention
Russia rejected a UK push to try to agree a resolution on Syria among permanent UN Security Council members on Wednesday, with Foreign Minister Sergei Lavrov saying the UN could not consider any draft resolution or proposed action in Syria before the UN weapons inspectors reported back.
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Models for possible intervention
- Iraq 1991: US-led global military coalition, anchored in international law; explicit mandate from UN Security Council to evict Iraqi forces from Kuwait
- Balkans 1990s: US arms supplied to anti-Serb resistance in Croatia and Bosnia in defiance of UN-mandated embargo; later US-led air campaign against Serb paramilitaries. In 1999, US jets provided bulk of 38,000 Nato sorties against Serbia to prevent massacres in Kosovo - legally controversial with UN Security Council resolutions linked to "enforcement measures"
- Somalia 1992-93: UN Security Council authorised creation of international force with aim of facilitating humanitarian supplies as Somali state failed. Gradual US military involvement without clear objective culminated in Black Hawk Down disaster in 1993. US troops pulled out
- Libya 2011: France and UK sought UN Security Council authorisation for humanitarian operation in Benghazi in 2011. Russia and China abstained but did not veto resolution. Air offensive continued until fall of Gaddafi
The use of force without a sanction of the UN Security Council would be a "crude violation" of international law and "lead to the long-term destabilisation of the situation in the country and the region", Mr Lavrov said.
The US state department criticised "Russian intransigence" and said it could not allow diplomatic paralysis to serve as a shield for the Syrian leadership.
UN 'moment' The UK, US and France are continuing their discussions following the meeting of the five permanent members.
The UK will want to be seen to be exhausting every diplomatic avenue, says the BBC's Nick Bryant at the UN headquarters in New York.
For the UK, there needs to be a UN "moment" - despite the fact that UN action will likely again be blocked by Russia or China.
But even without UN backing, the US and its allies have been clear that they see the military option is still open to them, our correspondent says.
"This is the first use of chemical warfare in the 21st Century," said UK Foreign Secretary William Hague. "It has to be unacceptable... or we will confront even bigger war crimes in the future."
More than 100,000 people are estimated to have died since the conflict erupted in Syria in March 2011, and the conflict has produced at least 1.7 million refugees.
Forces which could be used against Syria: - Four US destroyers - USS Gravely, USS Ramage, USS Barry and USS Mahan - are in the eastern Mediterranean, equipped with cruise missiles
- Cruise missiles could also be launched from submarines, including a British Trafalgar class boat. HMS Tireless was reportedly sighted in Gibraltar at the weekend
- Airbases at Incirlik and Izmir in Turkey, and in Jordan, could be used to carry out strikes
- Two aircraft carriers - USS Nimitz and USS Harry S Truman are in the wider region
- The Royal Navy's response force task group- which includes helicopter carrier HMS Illustrious and frigates HMS Montrose and HMS Westminster - is in the region on a previously-scheduled deployment
- RAF Akrotiri airbase in Cyprus could also be used
- French aircraft carrier Charles de Gaulle is currently in Toulon in the western Mediterranean
- French Raffale and Mirage aircraft can also operate from Al-Dhahra airbase in the UAE.
