Serbia warned on Thursday it would arrest the foreign minister of its former province of Kosovo for alleged terrorism if he turns up in Belgrade next week to attend a conference.

Hashim Thaci, who led a guerrilla insurgency against Serbia in the late 1990s, has been invited to the conference on reconciliation in the Serbian capital on April 24 and is "ready to go", an adviser said earlier.

"If he turns up in Belgrade, the Ministry of Interior will act according to the law and bring him to justice," Serbia's Tanjug state news agency quoted Interior Minister Nebojsa Stefanovic as saying.

Serbian politicians have long branded Thaci a war criminal for his role in Kosovo's 1990s conflict.

He was sentenced in absentia to 10 years in jail for "terrorism" by Serbia in 1997.

Thaci was a leader of the guerrilla Kosovo Liberation Army, which took up arms in the late 1990s after a decade of passive resistance to Serbian rule by Kosovo's ethnic Albanian majority.

Serbian forces began a counter-insurgency war, and NATO launched air strikes against Serbia in 1999 to halt massacres and expulsions of ethnic Albanian civilians.

In 2008 Thaci oversaw Kosovo's declaration of independence and for years has been involved in European Union-mediated negotiations aimed at settling relations with Belgrade.

Just last month, he shared coffee and a joke with his Serbian counterpart, Ivica Dacic, in Pristina.

Thaci has been invited to the regional conference on reconciliation in Belgrade organized by the Belgrade-based Youth Education Committee.

One of his advisers, Ardian Arifaj, told Reuters: "Thaci has received the invitation and is ready to go. Now it depends on the Belgrade authorities whether Thaci will go or not."

His arrest in Belgrade would represent a major diplomatic incident and anger the EU, which has invested much capital in trying to improve relations between Serbia and Kosovo, both of which want to join the bloc.

Serbia's war crimes prosecutor, Vladimir Vukcevic, said a further war crimes investigation against Thaci had been on hold as he was out of reach of the Serbian authorities.

But Vukcevic was quoted as telling the Serbian daily Blic: "if he comes here we can arrest him."