Foreign Secretary William Hague has spoke to the US Secretary of State John Kerry about developments in Syria, the Foreign Office confirmed tonight.
The talks came as condemnation of the alleged chemical attack drew more urgent calls for a UN investigation. There were tough words but still little agreement on how to deal with the escalating crisis, as Political Editor Tom Bradby reports.
France's foreign minister said the international community may have to use force if it is proven that Assad used chemical weapons in Syria in an attack the opposition says killed a thousand people.
The United States, Britain, France, Turkey and Saudi Arabia have all called for an urgent investigation into the attack and are urging Syria to allow UN inspectors access to the site.
Speaking on French radio he said:
His comments were echoed by Turkey's foreign minister Ahmet Davutoglu who said "all red lines have been crossed", referring to President Obama's comments last April when he said that Syria's use of chemical weapons would constitute a "red line."
In total 37 countries wrote to UN Secretary Genearl Ban Ki-moon to demand access to the site. German Foreign Minister Guido Westerwelle said: