The European Commission is to discuss in Brussels whether to recommend disciplinary proceedings against Poland over its planned judicial reforms.
The Commission is concerned that democracy in Poland is under threat from a raft of new laws, including how judges are appointed.
The Polish conservative government says the reforms are needed to curb inefficiency and corruption.
Thousands of people across the country have held protests against the reforms.
The European Commission has been monitoring the situation in Poland for almost two years.
Later on Wednesday, Commission President Jean-Claude Juncker will a lead a discussion about whether it is time to recommend the activation of the EU disciplinary process known as Article 7 – which has never been used before.
It could see Polish Prime Minister Mateusz Morawiecki hauled before his fellow leaders – who could insist on changes.
But no-one is considering what is seen as the “nuclear option” of suspending Poland’s voting rights at EU summits, the BBC’s Adam Fleming in Brussels reports.
This is because that would require all member states to agree – and Hungary has pledged to block such a move, our correspondent says.
The situation poses a potential diplomatic headache for British Prime Minister Theresa May who is due to meet her relatively new Polish counterpart at a summit in Warsaw on Thursday.
Mr Morawiecki has said that the EU has taken a one-sided view and that his country is entitled to carry out reforms.