WARSAW, Poland (AP) — European Council President Donald Tusk said Tuesday he wants an upcoming informal EU summit to assure participants that Europe can effectively defend its borders.

Tusk said that the “migration crisis” has exposed “weakness and chaos” in the EU’s border security.

He spoke in Warsaw following a meeting with Poland’s Prime Minister Beata Szydlo as he was sounding out opinion in EU capitals three days before the informal summit in Slovakia’s capital Bratislava. At the summit, prime ministers from the member states, except from the U.K., will discuss the EU’s future after Britain leaves.

Tusk, a former Polish prime minister who now chairs the meetings of EU leaders, said he was focused on European stability and would like the summit to convince its participants that “Europe is able to effectively control and defend its external borders.”

Szydlo’s spokesman, Rafal Bochenek, said that during their meeting the prime minister stressed that Poland will be pushing for a green light for deep political and economic reforms. She earlier said the EU might need to change its treaties, the documents regulating the way it functions.

Tusk said he was trying to convince Szydlo that Europe is “something worth being jointly taken care of rather than attacked or questioned.”

“Treaty changes in Europe may not necessarily serve Poland,” Tusk said. “All such destabilizing moves, revolutionary ideas, can rather be harmful to Poland.”

Poland and countries in central and eastern Europe have been insisting on bold reforms, including changes to the EU treaty. They say that the EU is authoritarian toward its member states, leaving no room for their own political decisions, and blame that for Britain’s decision to leave in a June referendum.

A major sticking point is that Poland and other countries in the region are refusing to accept set numbers of migrants under an EU plan. These countries insist that the EU’s external borders should be strengthened and protected, and that migrants should be helped in refugee camps close to their home countries.

Tusk also visited Hungary on Tuesday, meeting with Prime Minister Viktor Orban, who advocated for the adoption of “self-defensive immigration policies.” Hungary will hold a government-sponsored referendum on Oct. 2 in support of its opposition to any future EU plans to resettle refugees among the member states.

In a recent interview, Poland’s Szydlo said that if the EU is to be “saved,” its members “must introduce reforms, be bold and not afraid.”

Szydlo’s conservative government is at odds with the EU, which says Poland’s democracy and rule of law are threatened by the government’s push to influence a major court and give police more surveillance power. The government has retorted that EU bodies should focus on bigger EU problems.

The tensions also mar Szydlo’s relations with Tusk, as they represent Poland’s bitterly opposed political parties. The government accuses Tusk of failing to defend Poland’s interests in the EU.

Meanwhile, the European Parliament debated Poland’s rule of law ahead of a vote on the matter Wednesday.

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Raf Casert in Brussels and Pablo Gorondi in Budapest contributed to this report