The withdrawal of U.S. troops from Afghanistan from next July will begin with a general thinning out of forces rather than any large-scale drawdown, the commander of U.S. and NATO forces said on Tuesday.

Critics say U.S. President Barack Obama's strategy to begin pulling out troops has backfired, sending a signal to the Taliban that the United States was preparing to wind down at a time when U.S. and NATO forces were suffering record casualties. Five U.S. soldiers were killed on Tuesday, capping a bloody four days.

It has also alarmed Afghan leaders, a spokesman for President Hamid Karzai last week saying the Taliban threat has not been eliminated and any timeline for withdrawal would only invigorate the Islamist insurgents.

U.S. commanders have since tried to allay fears the timeline would not represent a wholesale departure.

The withdrawal timetable however is certain to come under close scrutiny when NATO members meet in Lisbon in November and in a White House strategy review of the Afghan war in December, which Obama called for last year when he announced the July 2011 plan and 30,000 extra troops.

Petraeus said the last of those extra troops would be in place in the next couple of days, taking the total number of foreign troops under the International Security Assistance Force (ISAF) umbrella in Afghanistan to almost 150,000.

He said guidelines had been drawn up for the transition and repeated the pace of withdrawals would depend on conditions on the ground, mainly security and the readiness of Afghan forces.

These guidelines recognise that this is a process, not an event, in other words it will typically represent a thinning out of ISAF forces, not a hand-off per se, Petraeus told Reuters and two other news agencies in Kabul.

In some cases, that transition dividend, in other words the forces no longer required, will go home, in some other cases they may be reinvested in a contiguous area, let's say within the same province to address security issues in neighbouring districts.

NATO NERVOUS

He said the transition will likely occur in districts initially rather than in entire provinces, adding this would likely not be possible in hard-fought areas.

The suggestion of transitions at the district level appeared to catch NATO slightly off guard. Secretary-General Anders Fogh Rasmussen said members had adopted documents based on responsibility being handed over province by province.

But this does not leave out that we can transfer a more limited responsibility, for example security responsibility, district by district, he told reporters in Copenhagen.

There is nervousness among Washington's NATO allies, who are coming under increasing pressure from a sceptical public to get out of a war they are not winning. Rasmussen said on Monday he hoped NATO states would agree in Lisbon to start handing over security responsibility next year.

Petraeus reiterated areas of progress were being made despite increasing violence across Afghanistan.

There's no question the Taliban are fighting back, but the toll on the Taliban leadership has been very hard, he said of recent campaigns in the south, east and north.

I don't think anyone disagrees that the footprint of the Taliban has spread, Petraeus said.

Military deaths have hit record levels this year, with at least 485 killed so far in 2010, compared with 521 in 2009.

ISAF said five U.S. troops had been killed on Tuesday, along with another on Monday whose nationality was not given. At least 20 ISAF service members have been killed since Saturday.

OPINION SPLIT

Supporters of Obama's July 2011 timeline say it conveys a needed sense of urgency to Kabul that Afghans must quickly ramp up the size of their security forces for a gradual handover.

But the strategy has certainly split U.S. opinion, even among Obama's Democrats, and will come under close scrutiny during mid-term Congressional elections in November.

Karzai's credibility will also come under scrutiny, particularly after a fraud-marred presidential vote last year.

While he is not running, Karzai's leadership will be tested at a parliamentary election on September 18, as will his commitment to good governance and stamping out rampant corruption.

Petraeus stepped cautiously around questions about Karzai's leadership, saying advances had been made since last year's poll.

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