Poland will uphold its veto on a European Union migration pact, its prime minister has said, as the bloc searches for agreement on a system for sharing out asylum-seekers who reach Europe outside of official border crossings.

"I am going to the European Council next week where I will uphold my veto on illegal migration," Mateusz Morawiecki said in a televised statement on Friday.

"This is an attempt to attack not only the sovereignty of Poland and other member states, but also an attempt to destabilise the EU in a non-democratic manner."

The EU's top migration official said the bloc was set to agree on how to handle irregular immigration soon after ministers' talks yielded no final deal on Thursday, with Berlin and Rome worried over rising arrivals ahead of key elections.

Poland's ruling Law and Justice (PiS) party also faces elections on Oct. 15 and one of its main campaign promises is to protect Poland from irregular immigration.

It announced a referendum on the issue on the same day as the vote.