UN investigators are due later on August 28 to collect more evidence of a possible chemical weapons attack on the outskirts of the Syrian capital amid growing signs Western powers are preparing possible military action against the regime of Bashar Assad.
On August 27, the chemical weapons inspectors did not visit sites of the alleged attack due to security concerns.
A day earlier, the UN team was fired on while traveling to one of the five sites around Damascus.
In Geneva on August 27, a UN spokesperson said the UN inspection team may need longer than the planned 14 days to complete its work and said their goal was to determine what chemical weapons might have been used.
Western powers have blamed Assad for the August 21 attack that killed hundreds of civilians and calls are growing for action to punish Damascus. Assad denies the claim and has received support from Moscow and Beijing.
U.S. Vice President Joe Biden said there was no question Assad was responsible for the attack.
"At President Obama's direction, all of us and his national security team have been in close touch with our foreign counterparts. The President believes, and I believe, that those who use chemical weapons against defenseless men, women and children, should, and must, be held accountable," Biden told a gathering of war veterans in Houston on August 27.
U.S. Defense Secretary Chuck Hagel told the BBC on August 27 that U.S. military forces are ready to strike Syria if President Barack Obama orders such action.
Analysts say planning appears to focus on missile or air strikes.
White House spokesman Jay Carney, said there is no question that chemical weapons had been used against Syrian civilians "on a massive scale."
“The options that we are considering are not about regime change. They are about responding to a clear violation of an international standard that prohibits the use of chemical weapons,” Carney told reporters in Washington on August 27.
Russia's Foreign Ministry on August 27 warned any possible military action could have "catastrophic consequences" for the region and called on the international community to show "prudence" over the crisis.
British Prime Minister David Cameron recalled Parliament to hold an emergency session on Syria on August 29.
"As I've said no decision has yet been taken, any decision would have to be proportionate, would have to be legal, would have to be about specifically deterring the use of chemical weapons. I've recalled Parliament so this issue can be properly debated so the government can listen to views in Parliament, and yes, it is my intention to put forward a motion to Parliament so members of Parliament will be able to vote," Cameron said.
French President Francois Hollande said he was "ready to punish" Assad for using chemical weapons.
"The chemical massacre in Damascus cannot be left without a response and France is ready to punish those who took the despicable decision to gas the innocent. In the last few days I have increased contact with our allies, notably [our] American and European [allies], as well as with our partners in the Arab world, to consider all the options," Hollande declared.
Syrian Foreign Minister Walid al-Moallem challenged Western powers to provide proof Damascus was behind the attack.
"[U.S. officials] said that the Syrian army used this weapon, although I have denied this to [U.S. Secretary of State John] Kerry. I say there is no country in the world that may use a massive destruction weapon against its people. I dare those who accuse our army to show the evidence that we used this weapon."
After meeting on August 27, officials of the Arab League issued a statement blaming the Assad regime for the attack and calling for UN Security Council action.
Based on AP and Reuters reporting