European Union officials are set to discuss whether to act on the bloc's threat to sanction the Polish government over its bid to exert control over national courts.
The EU last week warned the nationalist government in Warsaw against enacting new bills that would further undermine the judiciary's independence.
Polish President Andrzej Duda surprised many on Monday when he decided to veto two of the controversial bills, one of which would have reinforced political control over the Supreme Court.
Duda later signed into law a measure that allows the justice minister to hire and fire senior judges who head the common courts.
The ruling Law and Justice (PiS) party has vowed to press on with reforms, insisting the measures were necessary to make the judiciary more accountable.
With only one of the reforms adopted, it was not clear which steps, if any, EU First Vice President Frans Timmermans will announce on Wednesday.
The commission, the 28-nation EU executive, last week urged Poland to put the reforms on hold and warned it would "swiftly prepare infringement procedures for breach of EU law" against Warsaw.
Under these procedures, which will be debated on Wednesday, EU states can be hauled before the bloc's highest court and eventually be handed fines for the breaches.
On top of possible infringement proceedings, the commission said it was "very close to triggering Article 7", the bloc's never-before used "nuclear option" that can halt a country's right to vote in EU decision-making.
Ultimately, officials admit that Brussels is not fully prepared for events like those in Poland.
When the EU brought in Article 7 it was more as a backstop that had little chance of being used.
For Poland to be stripped of its voting rights in the EU, it would require unanimity from the 27 states.
But Hungarian Prime Minister Viktor Orban - whose own country has faced several legal threats from Brussels - vowed he would instantly veto any such move.
On Wednesday, the commission is likely to empower its president to launch legal cases against Poland should judges be sacked or presidential vetoes overturned.
In infringement proceedings, it does not need the backing of member states to sue a EU government at the European Court of Justice (ECJ).
If the ECJ were then to rule against Poland, Warsaw could face hefty daily financial penalties for not complying.
In 2012, the commission won a similar case against Hungary, whose government was trying to force out judges through early retirement.
Vera Jourova, EU justice commissioner, said 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".
For example, a country that is usually required to act on arrest warrants from another EU capital may now refuse to do so if it suspects the request is politically motivated, a senior EU official told the AFP news agency.
The PiS won elections in 2015 and its plans for judicial reforms triggered mass protests across Poland.