Belarusian President Alexander Lukashenko says he has warned Ukraine, against a background of rising tensions, not to try to drag his country into war.
With Russian forces struggling to advance and Ukraine raining drones on targets far inside Russia, Ukrainian President Volodymyr Zelenskiy has repeatedly alleged that the Kremlin wants to get Belarus more involved on the Russian side.
He raised the stakes last week by threatening to disable signal relay stations in Belarus that he said were helping Russian drones to hit Ukraine.
On Wednesday, he said the stations had stopped working although there was no independent confirmation.
Lukashenko, an ally of Russian President Vladimir Putin, said in televised comments that Zelenskiy's representatives had been in Minsk recently.
"I told them bluntly: 'Guys, tell your president: if he thinks he can talk to us like that - and drag us into a war to boot - then he needs to understand that the nature of the war would change instantly'," Lukashenko said, adding that Belarus had no desire to fight Ukrainian forces.
"We received a reply: the president and his team understand this. So, let's reach an agreement, guys. We need to reach a substantive agreement."
There was no immediate comment from Ukraine about Lukashenko's remarks.
Zelenskiy, writing on Telegram after meeting his foreign intelligence chief, Oleh Luhovskyi, repeated earlier comments that Belarus had upgraded roads in border areas and built up facilities for ammunition and fuel storage.
"Belarus knows what steps are needed on its part for peace," he wrote.
"The development of border infrastructure for aggression from Belarus must be stopped."
Belarus is strategically important to all sides, sharing borders with Russia, Ukraine and three NATO countries.
That significance was underlined last year when the United States re-engaged with Lukashenko after shunning contact with him for years, and began to ease sanctions on Belarus in return for the release of political prisoners.
The Kremlin on Thursday denied a Wall Street Journal report that Russia wanted to use Belarus as a springboard to step up attacks on Ukraine, and was threatening to cut financial support if it refused.
Kremlin spokesman Dmitry Peskov said the report "does not correspond to reality" and that Belarus was "our closest ally."
Belarusian Defence Minister Viktor Khrenin said it was members of the NATO military alliance that were stoking tension.
"The situation along our borders is extremely unstable, and escalating. Beyond our borders, NATO troop formations are being reinforced, infrastructure is being upgraded, the military budgets of neighbouring states are expanding, and politicians are making strident militaristic statements," he said in a speech to graduating officers.
"Efforts are under way to prolong, and even expand, the hot conflict unleashed by the West in Ukraine. Today, we are acutely aware of a blatant attempt to drag Belarus into the war."
European countries vehemently deny Russian allegations that they are responsible for the war in Ukraine, against which Russia launched a full-scale invasion in 2022.
While Lukashenko has not sent Belarusian troops to fight alongside Russia, he let Putin use Belarus as a launchpad to invade Ukraine and later agreed to let Russia station tactical nuclear missiles on Belarusian territory.
Belarus also conducts frequent joint military exercises with Russia and allows Russian forces to use its bases and training grounds.
