Nato has commanded the Isaf peacekeeping force since 2003

They will join 100 Polish soldiers already on the ground in Afghanistan, but will not arrive until February.

The announcement comes after Nato generals met on Wednesday to demand an extra 2,500 troops for the operation in southern Afghanistan.

Nato forces in the south are facing mounting casualties as they engage in fierce fighting with the Taleban.

But the BBC's Jonathan Marcus says Nato officials in Belgium are making it clear the Polish deployment will not provide the solution commanders had hoped for.

Our correspondent says they urgently need more troops before the onset of winter, when the fighting will slow down.

It is also unclear whether the Polish troops would be available to help the most dangerous part of the mission, in the south, our correspondent says.

There are at least 18,500 foreign, mainly Nato soldiers in Afghanistan in addition to about the same number of US troops deployed.

Half of them are in the south where Canadian and British forces are sharing the burden with US aircraft support and special forces on the ground.

In further clashes:

• Twelve Taleban and an Afghan policemen were killed in Helmand province in a joint operation involving the Afghan army, police and British troops, police said
• Taleban militants also raided governmental headquarters in Farah province, killing one policeman during hours of fighting, police said
• Four more policemen in the province died in an attack on their convoy

Maintaining momentum

The Nato commanders wanted a battalion of troops to make up a reserve force in Afghanistan - a battle group which could be moved around as required to help take more of an offensive against the Taleban, the BBC's Alastair Leithead in Kabul said.

Poland understands that Nato will have to be more active in Afghanistan - we are well aware of that, and that is why we decided to increase the size of the force Defence Ministry spokesman Leszek Laszczak

The fighting in southern Afghanistan continues to be intense and commanders there wanted reinforcements almost immediately to keep the momentum of their operations going and to help their mission, which they admit is stretched.

"We know this will be a dangerous operation," Polish defence ministry spokesman Leszek Laszczak said when announcing the extra troops.

"Poland understands that Nato will have to be more active in Afghanistan. We are well aware of that, and that is why we decided to increase the size of the force," Mr Laszczak added.

According to Defence Minister Radoslaw Sikorski, the Polish troops will primarily take part in operations in the east of Afghanistan.

Iraq question

Poland is a staunch ally of the United States and it currently has about 900 soldiers in Iraq, leading a multinational force south of Baghdad.

ISAF TROOPS IN AFGHANISTAN Total Isaf troops - 18,500 Contributing nations - 37 Isaf - International Security Assistance Force *A further 18,000 non-Isaf, US-led troops also in country Regional press concern Send us your comments

Mr Sikorski insists that even though Poland has indicated that it is set to reduce its troop numbers in Iraq, this further deployment to Afghanistan does not mean Poland is quitting Iraq.

"No decision has been made on that," Mr Sikorski said.

The announcement comes while Polish Prime Minister Jaroslaw Kaczynski is on a three-day visit to the US, which included a brief meeting with President George W Bush on Wednesday.

However, since the Polish troops will not be arriving until February, our Kabul correspondent says pressure will continue to be put on countries already supplying significant forces to Afghanistan, but which lack the political will to join the fighting in the south.