Secretary of State Hillary Rodham Clinton is trying to ramp up diplomatic efforts against President Bashar Assad's regime on a trip to North Africa this week, as some countries begin to explore the possibility of arming Syria's rebels.

Clinton is traveling to London on Wednesday for a conference on Somalia, but U.S. officials will be using the international gathering to lay the groundwork for a major conference on Syria's future taking place later this week in Tunisia. The trip comes as the Obama administration is opening the door slightly to international military assistance for Syria's armed opposition.

In coordinated messages, the White House and State Department said Tuesday they still hoped for a political solution. But faced with the daily onslaught by the Assad regime against Syrian civilians, officials dropped the administration's previous strident opposition to arming anti-regime forces. It remained unclear, though, what, if any, role the U.S. might play in providing such aid.