Turkish European Affairs Minister Ömer Çelik said on Monday that Turkey should reconsider part of its deal to keep migrants out of the European Union as tensions continue to escalate over a ban on Turkish ministers campaigning to expatriates in European countries for upcoming referendum in Turkey.

Speaking to the state-run Anadolu news agency, Çelik signaled that the Turkish government may take action against EU countries that banned Turkey’s ministers by threatening to loosen security measures on its borders with Europe and let thousands of migrants flow into the continent.

“I believe, especially the land passage component of the migrant deal with the European Union, should be reconsidered,” Çelik said.

A crisis erupted between Turkey and the Netherlands when The Hague canceled the flight clearance for Turkish Foreign Minister Mevlüt Çavuşoğlu’s airplane on Saturday and expelled Minister of Family and Social Policy Fatma Betül Sayan Kaya from the country, both of whom were coming to hold campaign rallies to seek the support of Turkish expatriates for a referendum that will switch Turkey to an executive presidency.

Earlier last week, Germany, Austria, Switzerland and Denmark canceled several rallies, planned to be participated in by Turkish ministers.

The agreement between Turkey and the EU signed on March 18 of last year sets out measures for reducing Europe’s worst migration crisis since World War II, including stepped-up checks by Turkey and the shipping back to Turkish territory of migrants who arrive in Greece.

In return, Turkey is slated to receive benefits including visa-free travel for its citizens to Europe, which in the accord was promised “at the latest” by June 2016. Turkey is also to receive up to the end of 2018 a total of 6 billion euros in financial aid for the over 2.7 million Syrian refugees it is hosting.

Turkey, however, has refused to revise its anti-terror laws, which Brussels insists are not compatible with European justice standards, thus deadlocking the visa liberalisation part of the deal.

Following a vote in the European Parliament in favor of freezing membership talks with Turkey last November, Turkey’s President Recep Tayyip Erdoğan has also threatened to open the border gates to Europe for millions of Syrian refugees.