Britain breathed a sigh of relief on Wednesday after it was granted a carve-out from President Trump’s 50 percent tariffs on steel and aluminum imported to the United States, while the rest of Europe fumed that it was now paying twice as much.

The exemption for British exports was granted because the country had already agreed to the framework of a trade deal, which was announced to much fanfare on May 8. But Britain’s steel industry is still frustrated that it faces 25 percent tariffs because the pact has yet to be put into place.

And Britain still faces the prospect of 50 percent tariffs on those goods starting July 9 if London has not ironed out a final deal with Washington.

“This is a time-bound vote of confidence for U.K. steelmaking and our industry’s ability to supply to the U.S. market, but in many ways also creates further uncertainty, which is disruptive,” said UK Steel, an industry trade group.

Some customers in the United States are still ordering semifinished steel from Marcegaglia Stainless Sheffield in Britain’s Midlands, said Christian Bruggmann, the company’s chief operating officer. Britain is better positioned than producers from other countries that have to pay the higher tariff, but the latest wrinkle “creates more uncertainty,” he added.

Some of Marcegaglia’s steel is processed through Sweden and Italy and would be subjected to the 50 percent tariffs. And company executives worry that Europe will be swamped by exports from countries like China and Indonesia, increasing competition for European steel. “The competition will be even worse,” Mr. Bruggmann said.