ZURICH (Reuters) - European Commission President Jean-Claude Juncker is concerned that a deal struck with Turkey in March on handling a wave of migrants bound for Europe could collapse, he told an Austrian newspaper.

European Commission President Jean-Claude Juncker chairs a meeting of the EU executive body in Brussels, Belgium, July 27, 2016. REUTERS/Francois Lenoir

“The risk is great. The success of the pact so far is fragile. (Turkish) President (Tayyip) Erdogan has several times hinted he wants to terminate the agreement,” Juncker told Kurier when asked if the pact could fall apart.

If that happened, “then you can expect that again refugees are standing at the gates of Europe,” he added in an interview published on Saturday.

Turkey has so far lived up to its side of the landmark deal with Brussels to stop illegal migration to Europe via its shores, in return for financial aid, the promise of visa-free travel to much of the bloc and accelerated talks on membership.

But Ankara has complained Europe is not living up to its side of the accord and has alarmed EU leaders by cracking down on Erdogan’s opponents, especially in the wake of a failed coup on July 15-16.

Juncker reiterated his concern about political developments in Turkey and repeated that any move by Ankara to introduce the death penalty would lead to the immediate breakdown of negotiations on joining the EU.

On other subjects, Juncker said he was concerned about the state of play in EU members as well.

“In Poland, the rule of law is being battered by the Polish government’s approach. Elsewhere there are incidents which go to the heart of democracy. I’ve been watching with concern preparations for the Hungarian refugee referendum,” he said, referring to a vote on whether to take in migrants.

“If referendums are now organized over every decision by the Council of Ministers and the EU Parliament, then the rule of law is in danger. The Commission would then actually - we are not there yet - open an infringement procedure against Hungary.”

Juncker said he was not looking forward to the possibility of dealing with French right-wing politician Marine Le Pen or U.S. Republican party nominee Donald Trump as presidents of their countries.

“I would not find that pleasant,” he said when asked how he would feel if Le Pen won the French presidential election next year and joined the ranks of European leaders. He added: “I trust in French common sense.”

And on Trump, whose America First campaign has stoked worries among European allies, he said: “I have never met him, and also put no increased value on meeting him permanently from January.”

He called Democratic president rival Hillary Clinton “a very serious and thoughtful woman”.