KABUL - The head of NATO said on Tuesday there would be no deadline for the exit of allied troops from Afghanistan, as fears grow among Afghans that foreign forces will leave before their own troops are able to guarantee security.

NATO Secretary-General Anders Fogh Rasmussen was visiting Afghanistan for the first time since U.S. President Barack Obama announced plans this month to send 30,000 extra troops to Afghanistan to try and tame mounting violence. NATO allies have also promised to send around 7,000 more.

But Washington's plan also calls for U.S. troop levels to be scaled down from 2011 as Afghan security forces gradually take over responsibility, sparking concerns among Afghan civilians.

Unrest has reached its worst levels in the eight-year war, and many fear that bombings and attacks may rise if their police and troops have not been well-enough prepared for their new responsibilities.

There are currently around 110,000 international troops in Afghanistan, including 68,000 Americans.

My first message is to the Afghan people: I know that some are wondering how long international forces will stay, more specifically, they are worried we will leave too soon, Rasmussen told reporters alongside the Afghan president in Kabul.

Let there be no doubt, the international community will stand with you, will protect you, and help rebuild your country until you are ready to stand on your own, he said.

Rasmussen said there would be a new momentum in 2010 as NATO ramped up its mission in Afghanistan but that its main focus would be to protect the population and train more Afghan forces.

Afghan police and soldiers would begin to take over security from foreign forces next year, he said, but stressed the change would only come when the Afghans were ready.

They will start to take the lead when and where they are ready. This transition will be conditions based, not calendar driven. We will stay the course, he said.

He added that NATO was now in a phase of increasing, not decreasing. But despite the headline figure of 7,000 extra forces, figures from NATO sources showed pledges for only 5,500 troops, with 1,500 more to be confirmed later.

Of the 5,500, at least 1,500 are already in the country and will not now be withdrawn as planned, NATO sources have said. The additional numbers also do not account for some 4,900 Dutch and Canadian troops due to leave Afghanistan in 2010 and 2011.

(Editing by Emma Graham-Harrison)