The European Union warned Poland on Wednesday it would "immediately" move to suspend its voting rights in the bloc if it pushes ahead with a mass sacking of supreme court judges.
President Andrzej Duda's unexpected vetoing of two controversial reforms, including one targeting the supreme court, had not ended the risk to the independence of the Polish judiciary, said Brussels.
European Commission Vice President Frans Timmermans has given Poland one month to reduce concern about the measures being pushed through by the right-wing government in Warsaw, or face sanctions.
The legal reforms have triggered mass street protests in Poland and raised fears for the rule of law in one of the EU's leading eastern former communist states.
"In this past week some things have changed in Poland -- and some things have not," Timmermans told reporters after European Commissioners met on the issue for the second week in a row.
Dutchman Timmermans said he "must acknowledge and welcome that president Duda has announced his decision to veto two of the four laws" but noted that two had already passed, and that the government would keep trying to push through the others.
Timmermans said the EU "asks the Polish authorities not to take any measure to dismiss or force the retirement of supreme court judges. If such a measure is taken the commission is ready to immediately trigger the Article 7 procedure."
Article 7 is a never-before-used EU process designed to uphold the rule of law, a so-called "nuclear option" that can freeze a country's right to vote in meetings of EU ministers.
Government to press ahead
Separately, the European Commission will launch legal action against Poland over one of the reforms that did go through, targeting the country's common courts, Timmermans said.
That could lead to Poland being hauled before the bloc's highest court and eventually given a fine.
Brussels and Warsaw have been at loggerheads over the legal changes ever since the right-wing Law and Justice (PiS) party took power in 2015 and announced reforms to Poland's constitutional court.
This month the government pushed through a bill that would have reinforced political control over the Supreme Court and another allowing parliament to choose members of a body designed to protect the independence of the courts.
Duda vetoed those two while signing into law another measure that allows the justice minister to unilaterally replace the chief justices of the common courts.
Polish Prime Minister Beata Szydlo has insisted that PiS will press ahead with the others.
While the EU's announcement on Wednesday marks a further raising of the stakes in its confrontation with Poland, the chances are slim that its voting rights could actually be suspended.
Populist Hungarian Prime Minister Viktor Orban has vowed he would instantly veto any such move by the EU.
The EU brought in Article 7 in response to fears about the rule of law in the wave of eastern states like Poland joining after 2004, although it was mainly intended as a backstop or threat that had little chance of being used.
EU Justice Commissioner Vera Jourova said Tuesday that the Polish crisis had caused a "very high level of nervosity" about whether it would "affect the whole EU system of mutual recognition of court decisions".