The first visit to Serbia for 68 years by an Albanian prime minister has turned into a diplomatic spat about the status of Kosovo, broadcast live on TV.
Edi Rama's historic trip to Belgrade was seen as an attempt to put differences aside after a football international was abandoned last month.
But tempers flared when Mr Rama said Kosovo's independence was "undeniable" and "must be respected".
Serbian PM Aleksandar Vucic hit back accusing him of a "provocation".
Kosovo, a former Serbian province with an ethnic Albanian majority, unilaterally declared independence in 2008.
Although many European nations and the US have recognised its independence, dozens of other countries do not, along with Serbia and the thousands of ethnic Serbs in Kosovo itself.
Simmering resentment between Albania and Serbia spilled over at last month's Euro 2016 qualifier in Belgrade.
Play was halted before half time when a drone appeared above the pitch, carrying an Albanian flag and a map of "greater Albania" showing nationalist claims on neighbouring states, including Serbia.
A Serbia player pulled down the flag and a brawl ensued during which several Albanian players were attacked by fans.
The Albanian prime minister was caught up in last month's row when Serbian media accused his brother of controlling the drone from the stadium's stands.
Mr Rama's visit had already been postponed because of the anger surrounding the match on both sides.
Then a news conference on Monday with his Serbian counterpart descended into both leaders trading barbs.
While both countries had completely different positions, Mr Rama said, the reality was "one and unchangeable".
"Independent Kosovo is an undeniable regional and European reality, and it must be respected," he insisted, provoking an angry response from Mr Vucic.
"I did not expect this provocation,'' the Serbian PM said. "What does Albania have to do with Kosovo? Kosovo is not part of Albania and it will never be.''
The exchange continued with Mr Vucic saying that nobody would humiliate Serbia and Mr Rama denying that his remarks were provocative.
The sooner Kosovo was recognised "the faster we can move on," the Albanian leader said.
Diplomats had tried to patch up relations after last month's brawl and Serbian radio station B92 reported that Mr Rama had spoken ahead of his trip of a new beginning for the Balkans.
The last such visit to Belgrade was when Albania's communist leader Enver Hoxha met Yugoslav President Josip Broz Tito in 1946.