U.S. Vice President Biden and Serbia's Prime Minister Vucic inspect honor guards in Belgrade Thomson Reuters BELGRADE (Reuters) - Hundreds of Serbian ultra-nationalists protested on Tuesday against U.S. Vice President Joe Biden's visit to Belgrade by chanting their support for the man he says is making the United States less safe - Donald Trump.

"Vote for Trump! Vote for Trump!" the protesters, wearing T-shirts displaying an image of the U.S. Republican candidate, shouted as they gathered near the Serbian presidency building.

Biden was on a one-day visit to Belgrade before traveling to Kosovo, with officials saying he will encourage both countries to do more to normalize their relations. Kosovo declared independence from Serbia in 2008.

The United States is highly popular among Kosovo's majority ethnic Albanians, who regard Washington as their savior for the U.S.-led NATO air strikes in 1999 that halted killings by Serbian forces waging a counter-insurgency war. But resentment still runs high in Serbia over NATO's intervention.

"Trump is the alternative to globalization. He will destroy old center of power in the United States and he is a supporter of Russia," Vojislav Seselj, head of Serbia's ultra-nationalist Radical Party, told Reuters when asked why he was backing Trump.

Biden, a Democrat, said on Monday that Trump's remark that President Barack Obama had founded Islamic State had increased threats to the physical safety of U.S. troops in Iraq.

At the time of the ultra-nationalist rally, Biden was in a government building in another part of Belgrade barred to protesters during his visit.

Trump's volatile campaign, which has included calls for a border wall with Mexico to keep out immigrants and a temporary ban on Muslims entering the United States, has pricked the interest of some right-wing and nationalist leaders abroad.

Seselj, who was acquitted in March of war crimes by the U.N. tribunal in The Hague, urged Serbian-Americans to vote for Trump in the November U.S. presidential election.

Victims of atrocities in Bosnia's 1992-95 war reacted with dismay in March to the acquittal of Seselj, who was accused of stoking murderous ethnic hatred with fiery rhetoric in the conflicts that accompanied federal Yugoslavia's break-up into seven successor states and killed 130,000 people.

Seselj's Radicals are the third largest party in the Serbian parliament.

(Reporting by Fedja Grulovic; writing by Ingrid Melander; editing by Mark Heinrich)