By Matt Falloon
LONDON (Reuters) - United States President Barack Obama and British Prime Minister David Cameron will step up their support for Syrian opposition groups this week and seek to map out the next phase for military operations in Afghanistan.
Cameron will fly to Washington on Tuesday eager to dispel concerns in Britain that its treasured "special relationship" with the United States has dimmed in recent years as Obama pivots U.S. foreign policy towards Asia.
In a joint editorial for Tuesday's Washington Post, the two leaders condemn "horrific violence against innocent civilians" by the government of Syrian President Bashar al-Assad and say they are seeking to prepare the ground for a change of power.
"With our international partners, we'll continue to tighten the noose around Assad and his cohorts, and we'll work with the opposition and United Nations-Arab League envoy Kofi Annan to plan for the transition that will follow Assad's departure from power," they say.
However, officials say there is unlikely to be much talk of arming rebel groups in Syria, with both leaders eager to stick to economic sanctions and diplomatic pressure.
The opposition Syrian National Council called on Monday for military intervention by Arab and Western governments, including a no-fly zone across Syria where the United Nations says government forces have bombed civilian areas as punishment for harboring rebels.
IRAN AND AFGHANISTAN
Obama and Cameron will also use this week's meetings to send a strong message to Iran to "meet its international obligations or face the consequences". The West believes Iran wants to build nuclear weapons, a charge denied by Tehran.
"We believe that there is time and space to pursue a diplomatic solution," they write.
On Afghanistan, the two leaders will prepare for the upcoming NATO summit in Chicago "to determine the next phase of transition", with officials saying the meeting will be crucial in ensuring the U.S. and Britain are in harmony on the timing of troop withdrawals.
"This includes shifting to a support role in advance of Afghans taking full responsibility for security in 2014 and ensuring that NATO maintains an enduring commitment," the editorial says.
Officials say their meetings are unlikely to result in a big shift in policy and will instead flesh out a plan to gradually withdraw troops over the next few years and to start a handover to Afghan forces.
The decade-long war in Afghanistan has grown increasingly unpopular in both the United States and Britain with the Taliban remaining a stubborn enemy, while the massacre of 16 villagers by a U.S. soldier on Sunday has fanned growing Afghan anger at the foreign presence.
Meanwhile British forces suffered their worst loss of life since 2006 last week when six soldiers were killed, taking the overall death toll over 400.
An opinion poll for Comres/ITV News on Monday showed nearly three quarters of Britons now think the Afghan war is unwinnable, up from 60 percent last year. More than half of Britons think UK troops should be withdrawn immediately.
Cameron's visit, designed to stress unity between the two leaders, is his second since coming to power in 2010. It includes a state dinner and a trip on Air Force One to attend a basketball game.
"The alliance between the United States and Great Britain is a partnership of the heart, bound by the history, traditions and values we share," they say in the Washington Post.
"But what makes our relationship special — a unique and essential asset, for our nations and the world — is that we join hands across so many endeavors. Put simply, we count on each other and the world counts on our alliance."
(Editing by Ben Harding)