BBC News with David Austin.

The United Nations is withdrawing all non-essential staff from Syria because the worsening conflict. UN Agency has been a key source of the humanitarian aid for hundreds of thousands of Syrians. Jim Muir reports.

Damascus is increasingly reassembling a city under siege, fighting around the international airport has halted practically all international flights for several days. With fighting taking place in many of the capital suburbs, the UN has announced is withdrawing all non-essential international staff and humanitarian missions outside Damascus will be halted for the time being. To compound the picture of the rapidly worsening situation, the Syrian Foreign Ministry spokesman Jihad Makdissi is reported to have already left the country even before reports that he had been dismissed, ostensibly for making statements out of the line with government policy.

The European has also said it reduced activities in the capital Damascus to a minimum. A White House spokesman, Jay Carney has said the US had increasingly concerned that Syria might be considering using chemical weapons in the conflicts with rebels. He said the US will be keeping a close eye on the Syrian government.

I think the President made clear that the use of the weapons was a red line. We are monitoring the situation in Syria closely, and we are monitoring the regime's chemical weapon stockpiles. We believe that with the regime's grip on power loosening, with its failure to put down the operation through conventional means, we have an increased concern about the possibility of the regime taking the desperate act of using its chemical weapons.