Sea change for Poland as Donald Tusk sworn in as PM

New Polish Prime Minister Donald Tusk's government was sworn in by the president on Wednesday, the final step in a transfer of power that marks a huge change after eight years of nationalist rule.

After years of disputes between Warsaw and Brussels under the previous government, led by the Law and Justice (PiS) party, the appointment of former European Council President Tusk has raised hopes of smoother relations with the rest of the European Union.

In a speech to parliament on Tuesday, Tusk vowed to secure billions of euros for Poland that have been frozen by the EU over concerns about the rule of law.

However, his task could be complicated by judges appointed under PiS reforms that critics said undermined the independence of the courts and by the power to veto laws held by President Andrzej Duda, a PiS ally.

"You have to be optimistic," Tusk told reporters as he set off for the swearing-in ceremony at the presidential palace. "I hope that we have common goals, even if we have different paths and experiences. Nobody has any doubts that we need to serve Poland."

Poland's Constitutional Tribunal ruled on Monday that judicial reform legislation that Poland needed to pass to access EU funds was unconstitutional.

It reached the same conclusion about penalties imposed by the EU's top court before it reaches a final ruling, known as interim measures.

Tusk is expected to travel to Brussels for an EU summit that takes place on Thursday and Friday.

In addition to trying to unblock funds for Poland, he will add his support to Ukraine's bid to eventually join the bloc.

With concerns growing in Kyiv about its Western allies' commitment to funding its defence against Russia's invasion, Tusk said on Tuesday that Poland would advocate for continued support.

Ukraine faces the possibility that Hungary will not give the green light for it to start EU accession talks at a Brussels summit.