By Phil Stewart and Missy Ryan
CHICAGO (Reuters) - Western leaders gathering this weekend to define their path out of Afghanistan will announce a pivot in the NATO mission next year, formally putting Afghan soldiers in charge of combat operations across the country, U.S. and NATO officials said on Sunday.
The leaders are expected to endorse a U.S. decision - telegraphed by the Pentagon earlier this year - to shift foreign troops to a support role in mid-2013.
"The milestone that we believe the leaders will consider tomorrow and that we anticipate that they will approve is a midway mile marker that marks a point in transition from NATO lead to Afghan lead," said Doug Lute, special assistant to President Barack Obama for Afghanistan and Pakistan.
NATO Secretary-General Anders Fogh Rasmussen said "by the middle of 2013, we expect the Afghan forces to be taking the lead for security right across the country."
While foreign forces will continue to fight the Taliban and other militants as necessary - and it may be very necessary - the new mission for U.S. and NATO troops will assume a new focus on advising and supporting Afghan soldiers.
The move is the latest step in what U.S. officials say is a steady military transition out of Afghanistan.
The White House, looking toward November elections, is seeking to dispel notions at this weekend's talks in President Barack Obama's home town that Western nations are rushing for the exits in Afghanistan.
It is a hard sell given the sharp fiscal pressures on nations fighting in Afghanistan and the emerging fissures with countries such as France that have embraced a quicker exit.
Under a plan agreed at their last summit in 2010, NATO nations said they would gradually transition out of Afghanistan by the end of 2014, meaning Afghanistan's inexperienced military will then spearhead the fight against Taliban insurgents.
While the expected announcement would confirm statements made earlier this year by Defense Secretary Leon Panetta, it underscores the eagerness of Western nations to disentangle themselves from a war that has lost much public support.
Obama foreshadowed the announcement during a middle-of-the-night visit this month to Kabul, where he signed a bilateral deal outlining the future U.S. presence in Afghanistan.
Obama said NATO would "set a goal for Afghan forces to be in the lead for combat operations" nationally in 2013.
"International troops will continue to train, advise and assist the Afghans, and fight alongside them when needed. But we will shift into a support role as Afghans step forward," he said in an address to the American people.
"This milestone is a way to gauge that we are track, rather than simply waiting until 31 December 2014," said Mark Jacobson, a senior fellow at the German Marshall Fund, who served as a senior NATO official in Afghanistan until last year.
TALIBAN VOWS TO FIGHT ON
U.S. commanders appear pleased about the developing abilities of Afghan forces, whose training and equipping has been a major focus of U.S. investment since 2009.
Afghanistan's security forces have grown to around 330,000. But they still lack key abilities in intelligence, air power, and logistics. A spate of attacks against foreign troops this year by Afghans in military uniforms has also raised questions about their loyalties and vulnerability to Taliban infiltration.
"No one expects the ANSF to ‘secure the country' a year from now," a U.S. defense official said, speaking on condition of anonymity.
General John Allen, the top U.S. and NATO commander in Afghanistan, dismissed speculation that NATO would halt combat operations once Afghans took the lead.
"That is not, in fact, correct," he said.
Afghan forces will not have an easy task when most of the NATO force, which now stands around 130,000, goes home. Taliban militants, able to renew their fighting power across the border in Pakistan, have promised to continue their fight until foreign forces have left Afghanistan.
"We must reiterate that the Mujahideen of Islamic Emirate will keep proceeding with their ongoing Jihad until it attains its goal," the Taliban, which refers to itself as an 'Islamic Emirate,' said in a statement issued for the NATO meeting.
When they conclude their discussions on Afghanistan on Monday, NATO leaders may also announce a formal end to their military mission in Afghanistan at the end of 2014 and establishment of a NATO training mission.
A modest number of Western troops are expected to stay in Afghanistan beyond then, focusing on targeted strikes on militants and advising Afghanistan's military.
(Additional reporting by Caren Bohan, Alister Bull and Matt Spetalnick; Editing by Warren Strobel and Christopher Wilson)