NATO has postponed a planned troop reduction in Kosovo as security in the Serb-dominated north remains "volatile", its secretary general Anders Fogh Rasmussen said Wednesday.

"We have, for the time being, postponed any decision to further reduce the number of KFOR troops in Kosovo" he told reporters on a visit.

"As long as the security situation in the north is volatile as it is, we have to maintain the current troop level... (of) 5,000 to 6,000 soldiers," he said during a visit to the breakaway territory.

Rasmussen was speaking at the end of a visit by NATO's governing body, the North Atlantic Council, to assess the security situation in Kosovo.

Kosovo unilaterally declared independence from Serbia in 2008 and is recognised by around 90 countries, but not by by Serbia, which has been encouraging some 120,000 local Serbs to defy the authorities in Pristina.

Tensions are particularly high in the north and its divided flashpoint city of Mitrovica, which has often seen violent clashes as local Serbs refuse to recognise the ethnic Albanian government in Pristina. Over the past year there has also been unrest on the border crossings between Kosovo and Serbia.

Tens of thousands of NATO-led peacekeeping forces (KFOR) have been deployed throughout Kosovo since the end of the 1998-1999 conflict between Serb armed forces and pro-independence Albanians.

Since early 2010, NATO has reduced its troop numbers from 15,000 to the current 6,000, intending until now to further cut the military presence in Kosovo to 2,500 this year, depending on security conditions.

Kosovo's government, meanwhile, on Wednesday offered participation of its security forces in NATO and other international peacekeeping operations, Prime Minister Hashim Thaci's office said in a press release.

The government had asked NATO to consider the possibility of "participation of units of the KSF (Kosovo Security Forces) or Kosovo police in operations out of the country, led by NATO or EU," it said.