Several Western leaders have indicated they're in no doubt Syrian forces have used chemical weapons on civilians.
The comments mark a significant escalation of a showdown over the attack outside the Syrian capital that killed possibly hundreds of people last week.
As Kerri Worthington reports, the rhetoric continues despite the Syrian government allowing United Nations inspectors to investigate the allegations.
The Syrian government has broadcast a statement on state television, saying the UN probe will prove that opposition claims of chemical weapons use against defenceless civilians are "lies".
"We have now received this statement by an official source at the foreign ministry: Today the Syrian Arab government and the United Nations have reached a common understanding during the visit of the UN high representative for disarmament, Ms Angela Kane. The understanding, which enters into force immediately, is about allowing the UN team to investigate allegations over the use of chemical weapons on 22 August, 2013."
The United Nations says its team will immediately start investigating what happened in the area, which is under rebel control.
But some international figures say Syria's overture has come too late.
British Foreign Secretary William Hague says Syrian President Bashar al-Assad's forces were responsible for the alleged attack and cannot be allowed to get away with it.
"If the regime believed somebody else had carried out this attack, then they would've given access to the UN inspectors several days ago. It was last Wednesday night when we and other countries called for that to the United Nations Security Council. They refused that up until now, they have continued to bombard with artillery the areas concerned, east of Damascus, which of course may have destroyed some of the evidence. So we have to be realistic now about what the UN team can achieve."
William Hague's French counterpart, Laurent Fabius has reiterated France's willingness to see military action against Syria.
"The massacre, the chemical massacre that has occurred in Syria and which the regime is evidently responsible for, is unacceptable. The position of France, which I hope is the position of all democracies, is that there must be a strong reaction."
And the mood in the United States, where any plan of action would have to originate, has shifted since Syrian opposition activists posted pictures of the alleged chemical attack on YouTube last week.
United States Republican senators John McCain and Lindsey Graham have long criticised President Barack Obama's failure to use military force against Syria.
The pair has again called on the US to rally its allies to take military action in Syria in order to change the balance of power on the ground and put an end to Bashar al-Assad's rule.
The top Democrat on the House Foreign Affairs Committee, Eliot Engel, speaking on US television, supported the call.
"I certainly would do cruise missile strikes. I think you can do that without boots on the ground, without having Americans in harm's way. You can destroy the runways, Assad's runways, you could destroy his munitions and you could destroy his fuel. There are lots and lots of things we could do. We could even destroy the Syrian air force if we wanted to."
There are signs President Obama may be getting ready to jettison his aversion to new Middle Eastern entanglements and to order limited military action.
There have been comments to that effect from the White House, a US diplomatic offensive and signs the US Defense Department is moving ships closer to Syria.
But Russia has reacted to the US manoeuvring by warning against making what it calls a "tragic mistake."
And Syria's Information Minister, Omran Zoabi, warned that US military action in Syria would have dangerous consequences for the region.
Mr Zoabi says any action would be unjust, as the West would be doing the bidding of opposition forces that the Syrian government calls terrorists.
"We've said it once, twice, and again we offer again our assurances that we have never used -- not in Ghouta nor anywhere else in Syria -- chemical weapons in any shape or form."
But the international medical aid agency Medecins Sans Frontieres, or Doctors Without Borders, says it does appear a neurotoxic substance has been used.
A spokesman, Christopher Stokes, says three hospitals near Damascus reported 355 deaths after the alleged chemical attack occurred last week.
"Since Wednesday we have been putting together a picture of what happened during that night. What they have told us and the information we have received is that 3,600 - approximately - patients were received and 355 died and a vast number of these patients presented symptoms that would be linked to a neurotoxic agent attack."
An Australian-based doctor and expert on managing victims of mass attacks agrees the available evidence shows some chemical agent was released.
Dr David Caldicott, an emergency doctor based at Calvary Health Care in Canberra, says the symptoms seen on the YouTube footage could be caused by a class of poisons known as 'organophosphates'.
He says several modern nerve gases including sarin are organophosphates, but they also form the basis of many widely available insecticides.
"I have to say it does look very similar to the sarin attack we saw in 1995 in Tokyo. If you wanted to mimic this sort of event for the purposes of political gain you could do so with any number of organophosphate insecticides. So while it's possible to say that it is likely that there has been a toxicological event, to say that it's been as a consequence of a military weapon is a longer bow to draw."
