BRUSSELS — Furious after President Trump pulled out of the Iran nuclear deal and reimposed punitive banking sanctions last year, European leaders vowed to find a way to enable Tehran to keep doing business with the rest of the world.

After months of delay, and after enduring mockery from the Trump administration, three major European allies on Thursday finally introduced a financial mechanism to do just that.

The question now is whether anyone will actually use it.

The new company, called Instex, for Instrument in Support of Trade Exchanges, would essentially allow goods to be bartered between Iranian companies and foreign ones without direct financial transactions or using the dollar. By avoiding the American banking system and currency, the hope is that European companies and others will feel confident that they can do business with Iran without being subject to the sanctions.

The European countries — Britain, France and Germany — were all signatories to the Iran deal in 2015, as was the United States under President Barack Obama. The Europeans, along with Russia and China, who were also signatories, have all vowed to keep to the terms of the agreement, which was intended to ensure that Iran could not build a nuclear weapon.