WASHINGTON, July 27, 2010 (AFP) – The general named to lead US forces in the Middle East said Tuesday US surge troops will be withdrawn from Afghanistan next year as conditions permit, assuring lawmakers it will "not be a handoff off of a hot potato."

General James Mattis, nominated to replace General David Petraeus as head of the US Central Command, warned that NATO forces will face months of difficult fighting and acknowledged they face a loss of credibility in the Taliban-dominated south.

Mattis said a July 2011 deadline set by President Barack Obama for starting to bring home the 30,000 additional US troops deployed to Afghanistan this year as only the start of a process that would be based on conditions on the ground.

"The idea is for a bottom-up, not a top-down, thinning out of our forces as we reach the conditions that permit a responsible turnover," he told the Senate Armed Services Committee.

"So again, it's a date when a process begins; it's not a handoff of a hot potato," he said.

Mattis, a Marine, was expected to easily win confirmation by the Senate.

He was tapped for the position after the US commander in Afghanistan, Stanley McChrystal, was fired for a magazine article in which he and his aides were quoted disparaging top White House officials.

Petraeus was named to succeed McChrystal, leaving open the Central Command, whose vast area of responsibility also includes Iraq, Iran, Pakistan and other Middle East hot spots.

Admired as a combat commander who led the first force of US Marines into Afghanistan after the September 11, 2001 attacks, Mattis went on to lead the marines in the 2003 invasion of Iraq and against Sunni insurgents in Anbar province.

But he got into trouble in 2005 for an on-camera interview in which he said it was "fun" to kill people.

"You go into Afghanistan; you've got guys who slap around women for five years because they didn't wear a veil. You know, guys like that ain't got no manhood left anyway, so it's a hell of a lot of fun to shoot them."