Syria chemical weapons: UN's Ban Ki-moon awaits report
UN Secretary General Ban Ki-moon says weapons inspectors investigating an apparent Syrian chemical attack will leave on Saturday and will then submit their report to him.
Hundreds are reported to have died in the attack near Damascus last week.
US President Barack Obama said he had not yet decided on a plan of action.
Other nations are also considering the next move. The UK wants a UN Security Council resolution to take "all necessary measures" to help civilians.
The UK prime minister's office said in a statement that the UK could still take "exceptional measures including targeted military intervention" even if the Security Council could not agree.
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".
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, a Chinese state-run newspaper has warned there are no excuses for air strikes on Syria.
The China Daily editorial accuses Western powers of acting as judge, jury and executioner before the UN has completed its investigation.
Russia, President 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.
Britain says it is sending six Typhoon fighter jets to Cyprus to protect British bases.
The UN weapons inspectors are now in their third day of investigations at the sites of an alleged chemical attack near Damascus.
Mr Ban 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 in Damascus on 21 August, which reportedly killed hundreds of people.
It accused the West of "inventing" excuses to launch a strike.
Many Damascus residents have fled the city in fear of an impending attack.
Long lines of cars loaded with suitcases have been waiting at the main Masnaa border crossing into Lebanon.
Lebanese officials told the Associated Press that at least 6,000 Syrians crossed into Lebanon in a 24-hour period in Masnaa, compared with 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 military strikes.
Mr 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 he said that the international norm against the use of chemical weapons "needs to be kept in place", and that he had concluded the Syrian government carried out the chemical weapons attack.
"We've looked at all the evidence, and we don't believe the opposition possessed chemical weapons of that sort," he said.
Critics say it is not clear what purpose a limited strike on Syria could serve.
But Mr Obama said it would send Mr Assad's government a "pretty strong signal" not to use chemical weapons again.
The BBC's David Willis in Washington 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 that he explain "the intended effect of military strikes", and how he would prevent the intervention escalating.
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.
Russia rejected a UK push to try to agree a resolution on Syria among permanent UN Security Council members on Wednesday.
Foreign Minister Sergei Lavrov said the UN could not consider any draft resolution or proposed action in Syria before the UN weapons inspectors reported back.
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.
The UK, US and France are continuing their discussions following the meeting of the five permanent members.
"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.