The United States says it has so far been unable to conclusively say whether chemical weapons were used in an alleged deadly gas attack in Syria.
State Department spokeswoman Jen Psaki said U.S. officials were doing everything possible to learn the facts about the alleged attack early on August 21 near Damascus.
She said President Barack Obama has directed U.S. intelligence agencies to work to help verify allegations made by opposition forces that Syrian government forces carried out the reported attack.
Meanwhile, UN Secretary-General Ban Ki-moon called on the Syrian government to allow UN weapons inspectors already in Damascus to investigate the reports "without delay."
A UN spokesman said Ban has urged the Syrian government to allow the UN experts access to the site of the alleged attack.
He also instructed UN High Representative for Disarmament Affairs Angela Kane to travel to Damascus.
The UN Security Council on August 21 backed an impartial and prompt investigation of the reported attack but did not say whether it should be done by UN experts who are currently in Syria.
President Bashar al-Assad's opponents gave death tolls ranging from several hundred to well over 1,000 for the August 21 attack near Damascus.
The Syrian government denies using chemical weapons.
Meanwhile, Syrian government forces continued to bombard the Damascus suburb that was allegedly hit by chemical weapons.
The British-based Syrian Observatory for Human Rights said mortar and rocket attacks resumed east of the capital on August 22.
On August 22, Turkish Foreign Minister Ahmet Davutoglu expressed frustration at the inaction of the UN Security Council.
"All red lines have been crossed but still the UN Security Council has not even been able to make a decision," he said. "This is the responsibility of the countries who are still setting these red lines and of all of us."
According to reports, Russia and China have opposed calling for an immediate UN-led probe. In the past, China and Russia have blocked UN Security Council resolutions calling for sanctions against Syria. Russia has been a long-time backer of the Assad regime, selling it advanced weapons systems.
French Foreign Minister Laurent Fabius told French radio and television that, in the absence of UN-approved action, it might be time for individual countries to consider a military response.
"If [the use of chemical weapons] is proven, the position of France is that there must be a reaction. What do I mean by saying a reaction? It is not to send soldiers into there, but a reaction -- of course, of international condemnation -- but a reaction which could take the form -- I don't want to be more precise -- of force."
WATCH: Amateur video appears to appears to show shelling in Damascus on August 21
Syrian Information Minister Omran Zoabi denied any involvement in the attack by the government, instead accusing rebel forces of "fabricating" the incident following successful operations by government troops.
"Everything that has been said is absurd, primitive, illogical, and fabricated," he said. "What we say is what we mean: There is no use of [chemical weapons] at all, at least not by the Syrian Army or the Syrian state, and it's easy to prove."
Video and other images distributed by opposition supporters -- whose authenticity could not be independently confirmed -- showed scores of victims, including many children. The victims did not have visible wounds or other injuries.
Some experts said sarin gas may have been involved. But it was not immediately known what toxic substances may have been used.
Russia has questioned the circumstances of the incident, suggesting it could have been a rebel "provocation.”
The UN team currently in Syria has a mandate to investigate allegations of previous chemical weapons use in the conflict.
Both sides have accused each other of using the weapons during their 30-month conflict.
With reporting by AP, AFP, and Reuters