BERLIN (Reuters) - The European Union could freeze member country Poland’s voting rights unless it changes course and agrees to stick to the rule of law, European Commission Vice President Jyrki Katainen said on Monday.

European Commission Vice-President Jyrki Katainen holds a news conference on the European Defence Action Plan in Brussels, Belgium November 30, 2016. REUTERS/Eric Vidal

Jaroslaw Kaczynski, head of Poland’s ruling Law and Justice (PiS) party, maintained his eurosceptic tone, however, telling a German newspaper he agreed with U.S. President Donald Trump’s view that the EU was primarily serving the interests of Germany.

Katainen told Reuters that he hoped German Chancellor Angela Merkel, who will meet with Polish leaders including Kaczynski in Warsaw on Tuesday, would help convince them to “follow the basic values on which the whole EU and Europe has been built”.

“We cannot make compromises on the rule of law. You either follow the rule of law or you don’t. If you don’t, then Europe cannot stay quiet,” Katainen, a former prime minister of Finland, said in an interview.

Poland could in theory be stripped of its EU voting rights if all other 27 member states saw fit, although Hungary, which also has a right-wing government that bristles against interference by Brussels, has said it would veto such a move.

But EU officials have said they feel they would have to at least attempt a vote if Poland does not back down over curbs on the media and changes to the constitutional court.

Katainen said the Polish government had “tested the limits” with its policies -- which critics say veer towards authoritarianism -- and encouraged EU members including Merkel to use their influence with Warsaw. He said the EU could be flexible in some areas, including fiscal policy, but that adherence to the rule of law was not negotiable.

Kaczynski meanwhile told the Frankfurter Allgemeine Zeitung newspaper that he welcomed Trump’s reluctance to get involved in other countries’ affairs, and was confident that the new U.S. president would not dismantle the NATO alliance.

“Much is unclear, but he has one advantage,” Kaczynski said of Trump. “He does not get involved in other countries’ affairs. Unlike (former U.S. President) Barack Obama, who criticized the status of constitutional affairs in Poland.”

Kaczynski called for EU members to challenge what he called German dominance of the 28-nation bloc. “Merkel is the absolute No. 1 in the EU and that is not a healthy situation,” he said.

At the same time, Kaczynski said he preferred Merkel, a conservative, to Martin Schulz, the former European Parliament leader who will challenge her in September elections.

He cited Schulz’s greater openness to Russia and criticized what he called the Social Democrat’s “lack of self-control.”

“He is a left-wing ideologue. Merkel has never expressed such anti-Polish views,” Kaczynski said.