BELGRADE (Reuters) - Serbia’s president said on Sunday that Kosovo had shown it wanted war with after it deployed special forces to prevent a train painted with Serbia’s national colors and the words “Kosovo is Serbia” from entering its territory.

FILE PHOTO - Serbia's President Tomislav Nikolic arrives for the Brdo-Brioni Process meeting, a gathering of political leaders from the Western Balkans, in Sarajevo, Bosnia and Herzegovina May 29, 2016. REUTERS/Dado Ruvic

President Tomislav Nikolic said the neighbors had been “on the brink of conflict” on Saturday, while Kosovo’s prime minister told reporters the train, a project of the Serbian government, sent “a message of occupation.”

Kosovo declared independence from Serbia in 2008 but Serbia still considers it part of its territory and supports a Serb minority there. NATO air strikes on Serbia forced Belgrade to withdraw its troops in 1999, having killed 10,000 Albanian civilians there. NATO still has around 5,000 troops stationed in Kosovo to keep the fragile peace.

The train left Belgrade for Kosovo’s northern town of Mitrovica on Saturday, but stopped while still in Serbia after Pristina said it had deployed special forces to prevent the train from crossing its border. [nL5N1F40GU]

Following a specially convened National Security Council’s session, Nikolic said that by sending special police forces “Albanians showed they want the war.”

“We were on the brink of the conflict yesterday,” Nikolic said.

Kosovo’s Prime Minister Isa Mustafa said the move had been an act of protecting Kosovo’s sovereignty.

“The institutions of the Republic of Kosovo will always undertake such actions to protect the country’s sovereignty and not allow machines that will provoke with a message of occupation,” Mustafa told reporters outside Pristina.

Relations between Belgrade and Pristina came under renewed strain on Jan. 4 when former Kosovo prime minister Ramush Haradinaj was arrested in France on a warrant from Serbia which accuses him of war crimes. [nL5N1EU4GB]

Kosovo Albanians make up more than 90 percent of Kosovo’s 1.8 million population. Northern Kosovo, where Mitrovica is situated, is home to a Serb minority of around 40,000 to 50,000 people who do not see Pristina as their capital.

Normalizing relations between Kosovo and Serbia is key condition for both countries to progress towards membership in the European Union both governments are aiming for.

In 2013 Belgrade and Pristina opened an EU-mediated dialogue to normalize relations, but Serbia is still blocking Kosovo’s membership in international organizations including the United Nations.