The EU is set to launch legal actiona against Poland, Hungard and the Czech Republic for failing to take in their share of refugees as agreed at a Europe-wide level

The EU will this week launch legal action against Hungary, Poland and the Czech Republic for refusing to take in their share of refugees under a controversial solidarity plan, diplomats said Monday.

Brussels last month set a June deadline for Warsaw and Budapest to start accepting migrants under the 2015 plan to ease the burden on frontline states Italy and Greece, or risk sanctions.

Prague also came under pressure after effectively dropping out of the scheme to relocate 160,000 refugees, which was agreed on at the height of the migrant crisis.

"Our expectation is the infringement procedure will be started," an EU diplomat told AFP.

Three diplomats told AFP they expected Poland and Hungary to face sanctions as well as the Czech Republic, which had made no new pledges after having failed to take in any asylum seekers for a year.

European Commission chief Jean-Claude Juncker and his team of commissioners are expected to make a decision when they meet on Tuesday, with a formal announcement on Wednesday.

Juncker -- who has repeatedly criticised Eastern European states for failing to take their fair share -- had threatened Friday to launch such action.

"Next week, we will address the question of whether to launch treaty violation proceedings or not," Juncker told Germany's Spiegel weekly. "The decision has not been made, but I say that I am for it."

Commission spokeswoman Mina Andreeva told AFP the commissioners "will discuss the matter" Tuesday and that no decision had been taken yet.

Under "infringement" proceedings the European Commission, the 28-nation EU's executive arm, sends a letter to national governments demanding legal explanations over certain issues, before possibly referring them to the European Court of Justice.

EU states can eventually face stiff financial penalties if they fail to comply.

Eastern European countries including Hungary and Poland have rejected outright the "relocation plan" adopted in 2015 to redistribute among other member states 160,000 mainly Syrian, Eritrean and Iraq asylum seekers from Greece and Italy by September.

By the start of June, less than 20,000 people had been relocated under the plan, which was in response to Europe's biggest ever migration crisis.

European sources have blamed the delays on a series of factors: governments trying to screen jihadists in the wake of terror attacks, a lack of housing and education for asylum seekers, and logistical problems.

They said some countries were setting unacceptable conditions by refusing Muslims, black people or large families, with Eastern European states the worst for discriminating on religious or racial grounds.