BRUSSELS — European Union authorities discussed a provocative proposal Tuesday to require that United States and Canadian citizens obtain visas to travel to Europe, but they delayed a decision on the matter until summer.

In a measure of the delicate nature of the topic for trans-Atlantic relations, the European Commission, the European Union’s executive arm, set a July 12 deadline for the European Parliament and the bloc’s 28 member governments to offer advice on next steps.

After that deadline, the commission could start the process of imposing visa requirements for Americans and Canadians. But any change would not go into effect immediately, because a majority of governments, and the European Parliament, would have six months to block the move.

“E.U. citizens rightly expect to travel without a visa to any third country whose citizens can enter the Schengen area visa-free,” Dimitris Avramopoulos, the European commissioner for citizenship and migration, said after the meeting in Strasbourg, France.