U.S. Secretary of State John Kerry hosts his British counterpart William Hague for talks Wednesday in Washington focused on the situation in Syria.
The meeting comes as both nations consider potential steps to achieve their goal of establishing a transitional government in Syria to lead the country out of more than two years of turmoil.
Both Britain and the United States have provided non-lethal support to rebels opposed to Syrian President Bashar al-Assad, and have discussed the possibility of sending weapons.
The White House said Tuesday that arming the rebels remains one option President Barack Obama is considering as he weighs a range of possible actions related to Syria.
White House Press Secretary Jay Carney said the United States and its international partners continue to pursue a Syrian peace conference, but that the ongoing violence means they must also explore aiding the opposition.
He declined to give guidance on when any decision will be made, emphasizing that national security leaders are regularly discussing the situation.
Obama has ruled out any intervention that would require U.S. military forces inside Syria.
Meanwhile, Human Rights Watch is urging both the opposition and the Syrian government to allow humanitarian aid to freely flow to civilians inside Syria.
The group said Wednesday the United Nations must also do more to help get aid across the border from Turkey into northern Syria.
Human Rights Watch says it visited several northern provinces between December and April, and found civilians in need of food and medical aid.
The group wants the United Nations to facilitate the work of non-governmental organizations who can provide the aid, or for the U.N. to use its own resources to get needed supplies into Syria.
It also highlighted the challenges humanitarian groups are facing, both with Syrian bureaucracy that keeps aid from reaching opposition-held areas and with safely navigating aid through the multitude of rebel groups.