Clinton on mission to boost diplomatic efforts against Syria.

AP - Secretary of State Hillary Rodham Clinton is trying to push diplomatic efforts against President Bashar al-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 travelling 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 co-ordinated 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.

"We don't want to take actions that would contribute to the further militarization of Syria because that could take the country down a dangerous path," White House press secretary Jay Carney told reporters. "But we don't rule out additional measures if the international community should wait too long and not take the kind of action that needs to be taken."

The administration had previously said flatly that more weapons were not the answer to the Syrian situation. There had been no mention of "additional measures," despite daily reports from Syrian activists of dozens of deaths from government attacks.

At the State Department, spokeswoman Victoria Nuland used nearly identical language to describe the administration's evolving position.

"From our perspective, we don't believe that it makes sense to contribute now to the further militarization of Syria," she told reporters. "What we don't want to see is the spiral of violence increase. That said, if we can't get Assad to yield to the pressure that we are all bringing to bear, we may have to consider additional measures."

Neither Carney nor Nuland would elaborate on what "additional measures" might be taken but there have been growing calls, including from some in Congress, for the international community to arm the rebels. Most suggestions to that effect have foreseen Arab nations such as Qatar, the United Arab Emirates and Saudi Arabia — and not the West — possibly providing military assistance.

Clinton's trip to Europe and North Africa is taking place amid increased international discussion about adding a military component to the package of humanitarian and political aid to the opposition that will be the focus in Tunisia.

More than 70 countries have been invited to Friday's "Friends of Syria" meeting, which follows the failure of the UN Security Council to endorse an Arab plan that would have seen Assad removed from power.

U.S. officials say it won't produce decisions on military aid or even recognition of Syria's disparate opposition groups, but countries are considering creating large stockpiles of humanitarian aid along Syria's borders.

Discussion of military assistance is still preliminary, said the officials, who spoke on condition of anonymity due to the sensitive nature of the diplomacy. To maintain the pressure against Assad, Washington is trying to keep as many countries as possible involved in the international co-ordination against Syria's government — even if there is no consensus on arming the rebels.

This week's talks will seek to clarify some of the confusion. The U.S. is trying to get a clearer picture of what promises countries such as Syria's Arab neighbours are making to elements of the opposition, which rebels each government might support and some agreement on what types of assistance would be helpful or damaging.

The backdrop to the discussions is the heightening fear that Syria could descend into an all-out civil war.