WARSAW/BRUSSELS (Reuters) - Poland’s euroskeptic government urged other EU states on Wednesday not to reappoint Donald Tusk, a former Polish prime minister, as chairman of the European Council, saying it would further damage the fragile unity of the bloc.

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But diplomats said European Union leaders were virtually certain to extend Tusk’s mandate by a further 30 months when they meet on Thursday in Brussels. The European Council groups the EU’s 28 national leaders.

Poland’s ruling right-wing Law and Justice party (PiS) accuses Tusk, a soft-spoken centrist, of overstepping his mandate by, for example, criticizing the Warsaw government during its standoff with the opposition over media freedom.

Tusk and PiS leader Jaroslaw Kaczynski are also long-standing bitter rivals in Polish politics.

“We cannot allow the creation of such a dangerous precedent whereby a democratically-elected government in a member state comes under political attack from the president of the European Council,” Polish Prime Minister Beata Szydlo said in a letter to the other EU leaders.

Tusk dismissed the accusation of political bias in his current job, though he said he also had a responsibility as Council chair to defend European values. The EU has accused the PiS government of undermining Polish democracy.

“I am, and I should be also in the future, impartial and politically neutral versus all 28 member states,” Tusk told reporters on Wednesday.

“LARGE SUPPORT” FOR TUSK

Poland hopes to be able to delay a decision on Tusk beyond Thursday, potentially opening the way to horse-trading and agreement on another candidate, diplomats say. Last week Warsaw proposed a Polish member of the European Parliament, Jacek Saryusz-Wolski, to replace Tusk.

But EU diplomats said Tusk’s reappointment was virtually guaranteed, noting that the bloc had enough problems already, including Brexit, the migration crisis, an assertive Russia and the new U.S. administration of Donald Trump.

“The renewal of Tusk’s mandate has very large support,” said one senior EU diplomat.

Tusk is seen as a safe pair of hands and has earned respect with his smooth handling of issues such as Britain’s shock vote last summer to leave the EU. As Council president he is expected to play a key role in the looming Brexit negotiations.

Joseph Muscat, prime minister of Malta, current president of the EU, will oversee Thursday’s discussion on extending Tusk’s mandate and a simple majority will be enough to re-elect him.

The enmity between Tusk and Kaczynski, who both began their political careers during the underground struggle against communism in Poland, goes back many years.

Kaczynski holds Tusk “morally responsible” for the death of his twin brother, President Lech Kaczynski, in a plane crash in Russia in 2010, when Tusk was prime minister. Polish and Russian investigations blamed pilot error.