William Hague will make a statement to MPs on Syria after the United Nations failed to agree a resolution demanding an end to the bloodshed.
The Foreign Secretary is to set out Britain's position amid widespread criticism of Russia and China for vetoing the latest text.
Mr Hague indicated on Sunday that the UK would seriously consider severing diplomatic ties with Damascus if the Arab League followed Tunisia in expelling Syrian ambassadors. But he insisted that military action was not being considered.
There have been more reports of violence as the 11-month crackdown on pro-democracy protests continues.
One of the bloodiest bombardments yet came just hours before the diplomatic deadlock at the UN on Saturday - with up to 200 people reported dead in the city of Homs.
Mr Hague conceded that the country appears to be slipping towards all-out civil war between anti-regime groups and the security forces controlled by President Bashar Assad.
He also warned that Russia and China would bear some responsibility for future casualties following their refusal to back an Arab-led peace plan.
But he said the way forward was for the Arab League, with the backing of Western nations, to "intensify their own pressure on the Assad regime to stop the killing and allow a peaceful transition".
He said the UK would hold talks with Arab League member states ahead of a meeting of their foreign ministers this week. Russia's foreign minister is due in Damascus on Tuesday.
The Foreign Secretary is expected to deliver his statement to MPs after 3pm.