The US wants allies to contribute $1 billion each year to help fund Afghanistan's security forces after the planned exit of foreign troops by the end of 2014, Poland's foreign minister said Thursday.

Speaking in Warsaw, Radoslaw Sikorski said Poland could be asked to contribute up to $20 million (25 million euros) each year.

"Our government is currently verifying our capacities," he said.

The US expects countries participating in the International Security Assistance Force (ISAF) to help fund Afghan security forces.

Sikorski said the total cost of funding security operations could rise to about $4 billion (five billion euros) in the coming years.

An ex-communist country that joined NATO in 1999, Poland currently has around 2,500 troops deployed in the ISAF force.

Afghan forces are gradually taking over the country's security, with a goal of letting most of the 130,000 foreign troops leave by the end of 2014.

Officials from Kabul will attend NATO's upcoming summit in Chicago in the hope of securing funding.