The United States has asked NATO allies to do their fair share in Afghanistan by sending more forces to provide security for a presidential election in August, but has received only a limited response.
US Defence Secretary Robert Gates said he would not seek a specific number of extra troops from a NATO defence ministers' meeting in Krakow, but called for a short-term deployment of troops from the alliance's rapid response force, which has never been used.
US President Barack Obama authorised 17,000 more American troops for Afghanistan this week, taking the US contingent to around 55,000.
Some 40 other countries, most of them in NATO, have provided 30,000 troops.
NATO Secretary-General Jaap de Hoop Scheffer said there was a strong commitment among allies to ensure sufficient forces for the election, but European allies have responded to pleas for more troops with pledges in the hundreds, not thousands.
Italy said on Wednesday it would send 500 more troops by April and Germany confirmed a pledge of 600 more soldiers.
Germany, which has long resisted calls for it to remove restrictions on the way its own forces can be used in Afghanistan, said the rapid response force should not be used for Afghan duty.
Britain, with the second largest force in Afghanistan, said it was up to other NATO states to step up their commitments.
