President Alexander Lukashenko said on Monday Belarus seeks no confrontation with Poland but wants the European Union to take in 2,000 of the migrants stranded on its border, and he added that if the crisis deteriorated "too far, war is unavoidable".
The European Union accuses Belarus of flying in thousands of people from the Middle East and pushing them to cross into the EU via Poland, Lithuania and Latvia in retaliation for EU sanctions imposed on Minsk over Lukashenko's crushing of protests against his disputed re-election last year.
Lukashenko denies fomenting the migrant crisis, but EU countries including Germany on Monday again rejected his call on them to accept migrants in limbo at the frontier.
Polish Prime Minister Mateusz Morawiecki said on Sunday that the crisis might be a prelude to "something much worse", and Poland's border guard said Belarusian forces were still ferrying migrants to the frontier.
Lukashenko, as quoted by the state-owned Belta news agency, said he did not want things to escalate.
"We need to get through to the Poles, to every Pole, and show them that we're not barbarians, that we don't want confrontation. We don't need it. Because we understand that if we go too far, war is unavoidable," he said.
"And that will be a catastrophe. We understand this perfectly well. We don't want any kind of flare-up."
The plan proposed by Belarus last week would entail EU countries, particularly Germany, taking in some 2,000 migrants, while Minsk would send another 5,000 migrants back home, and Lukashenko said Belarus was preparing a second migrant repatriation flight at the end of this month.
In the face of a rebuff from Germany and the EU's executive commission, Lukashenko said on Monday he must insist Germany - the preferred destination of many migrants - take in a number of them. He said the EU was not engaging with Minsk on the issue.
"They don't even look at it (the problem). And even what she (German Chancellor Angela Merkel) promised me - contacts. They are not even getting in touch."
But a German government spokesman repeated Berlin's refusal.
"The idea of having a humanitarian corridor to Germany for 2,000 migrants is not a solution that is acceptable to Germany or the EU," the spokesperson said.
Austrian Chancellor Alexander Schallenberg told a news conference: "The EU must not give in to blackmail from Lukashenko. We have to respond united and very clearly to this state-sponsored hybrid attack on the European Union."
A group of around 150 migrants tried to break through the border fence near the Polish village of Dubicze Cerkiewne on Sunday, the Polish border guard said.
Poland has threatened to sever a train link with Belarus if the situation does not improve, and Lukashenko was quoted as saying that threat could backfire.
Rail traffic could be diverted to run through a conflict zone in eastern Ukraine in such a scenario, he said.
"It is Mr Lukashenko and the Belarusian regime that caused the entire problem at the border...It is up to Mr Lukashenko what will happen next," Polish Deputy Foreign Minister Marcin Przydacz said. "The EU...can find a way to trade with eastern European and Asian partners without Belarus."
The Polish Economic Institute (PIE) said any closure of the border to train freight would be more costly for Belarus as exports account for up to 70% of its gross domestic product.
Poland's government spokesman said no decision had been taken on the closure, though that option was on the table.
Humanitarian agencies say as many as 13 migrants have died at the border, where many have suffered in a cold, damp forest with little food or water as a frigid winter sets in.
Poland said Belarusian forces were still ferrying migrants to the frontier, despite clearing the main migrant camps along the barbed-wire boundary last week. Many of the migrants have now been placed in a Belarusian warehouse near the border.