UN ignores EU calls for Syria inspections

British foreign minister William Hague and France's Laurent Fabius had earlier called for direct UN access to the site of the alleged war crime after meeting Ahmed al-Jarba, the head of the Syrian National Coalition, a leading rebel group, in Paris.

Fabius said al-Jarba claimed that 1,200 people were killed in the assault earlier on Wednesday in a Damascus suburb.

"I told him we have asked the security council to require the mission of Dr. Ake Sellstrom, which is currently present in Damascus, to be granted immediate access in order to establish the facts," the French minister said.

An earlier EU statement, issued by foreign policy chief Catherine Ashton, also noted: "Such accusations should be immediately and thoroughly investigated by the United Nations expert mission, which arrived recently in Syria."

For their part, US diplomats circulated a text of a draft UN statement which, they said, was watered down by Syria's allies in the UN body, China and Russia.

The draft text had called for the UN to "urgently take the steps necessary for today's attack to be investigated by the UN mission on the ground."

The Sellstrom mission arrived in Syria on Sunday.

But, following five months of negotiations on its mandate with the Syrian authorities, its actions will be limited to looking at three locations linked to 13 earlier allegations of chemical weapons use.

Meanwhile, Israel and Turkey have given credence to the rebels' new claims.

But Russia, as well as Syria's other main ally, Iran, have said the latest incident is a "provocation" staged by rebels in order to prompt Western military intervention.

The allegations were supported by videos posted by rebel groups on YouTube.

The videos show scores of dead bodies wrapped in shrouds in makeshift clinics, as well as men and children suffering from convulsions and disorientation.

The alleged attack took place one year - almost to the day - after US President Barack Obama said that large scale use of chemical arms is a "red line" for US action.

A White House statement on Wednesday made no mention of the red line, however.

"If the Syrian government has nothing to hide and is truly committed to an impartial and credible investigation of chemical weapons use in Syria, it will facilitate the UN team’s immediate and unfettered access to this site," White House spokesman Josh Earnest said instead.

"I’m not talking about red lines. I’m not having a debate or conversation about red lines or I’m not setting red lines. Let's talk, not talk, about red today," state department spokeswoman Jen Psaki told press.

The US also leaked a letter to the Associated Press news agency sent by its military chief, Martin Dempsey, to a US congressman, Eliot Engel, on 19 August, which spells out why it does not want to get involved.

Dempsey said that if the US destroyed Syria's air force it would "would not be militarily decisive, but it would commit us decisively to the conflict."

He noted: "The use of US military force can change the military balance … but it cannot resolve the underlying and historic ethnic, religious and tribal issues that are fueling this conflict."

He added: "It is my belief that the side we choose must be ready to promote their interests and ours when the balance shifts in their favour. Today, they are not."