ABOARD AIR FORCE ONE (Reuters) -- The United States is disappointed that Damascus has failed to live up to promises made to adhere to a UN-backed peace plan and will increase pressure on Syrian President Bashar Assad, White House spokesman Josh Earnest said Friday.

"We intend to continue to ramp up the international pressure against the Assad regime and encourage them in the strongest possible terms to live up to the obligations and commitments that they made in the context of the Kofi Annan plan," Earnest told reporters aboard Air Force One.