Poland threatened to scupper a summit of EU leaders if Warsaw was forced to vote on the reappointment of European Council president Donald Tusk.
The row comes as nearly all other EU countries, including close allies of Warsaw such as Hungary, backed Mr Tusk’s attempt to be given another 30 month term in the top job.
Warsaw has opposed giving Mr Tusk another term in the role, accusing the former Polish prime minister of interfering in domestic affairs.
Mr Tusk was a staunch opponent of the ruling Law and Justice party in his former job.
Polish foreign minister Witold Waszczykowski told Polish TV that Warsaw would be happy to hinder the meeting of heads of government if a vote on Mr Tusk is pushed through.
“There’s no need to pick in a hurry,” he said. “We will do everything so that there’s no vote. We will be making clear that the summit is in danger.”
Britain is considering abstaining on the vote, according to influential German MEP Manfred Weber. A spokesperson for the British government said that Theresa May will decide during the private meeting whether to back Mr Tusk.
Poland alone cannot block the reappointment of Mr Tusk. Warsaw’s opposition has created a delicate diplomatic situation in that a senior EU role will be filled by someone against the wishes of their home country.