WARSAW, Poland (AP) — The Trump administration lashed out at some of America’s closest traditional allies on Thursday, accusing Britain, France and Germany of trying to “break” U.S. sanctions against Iran and calling on European nations to join the United States in withdrawing from the landmark 2015 Iranian nuclear deal.

In an unusually blunt speech to a Middle East conference in Poland, Vice President Mike Pence slammed the three countries and the European Union as a whole for remaining parties to the agreement after the Trump administration withdrew from it last year and re-imposed tough sanctions on Iran.

The harsh criticism threatened to further chill U.S.-European ties, already badly strained, including over the Iran focus of the Warsaw conference, co-hosted by the U.S. and Poland. France and Germany had declined to send their top diplomats to the foreign minister-level meeting and E.U. foreign policy chief Federica Mogherini also stayed away.