US Secretary of State John Kerry was in London on Monday on the latest leg of a tour to garner support for US-led military action in Syria.
Kerry was due to meet British Foreign Secretary William Hague and Palestinian President Mahmoud Abbas in London.
The British parliament voted against military intervention in Syria last week.
Kerry arrived from meetings in Paris with the Arab League, which did not endorse a strike by the West, stressing instead the need for a political solution to the 29-month conflict in Syria.
He met EU foreign ministers in Lithuania on Saturday, when the bloc called for a “clear and strong response” to the alleged use of chemical weapons in Syria.
Syrian President Bashar al-Assad denied Sunday he had anything to do with the alleged chemical weapons attack near Damascus on August 21, in excerpts of an interview on PBS. The full interview will be broadcast later Monday.