Britain is parting company with the European Union by not retaliating to the tariffs that President Trump imposed on steel and aluminum imports on Wednesday, as Prime Minister Keir Starmer calculates that he can negotiate a trade deal with the United States that would spare his country in the long term.

The approach contrasts sharply with that of the European Union, which hit back swiftly with retaliatory measures on American exports, including Harley-Davidson motorcycles, bourbon and jeans, and top European officials have warned about the uncertainty Mr. Trump’s policies are causing. By contrast, British officials have expressed only muted disappointment that they have been swept into Mr. Trump’s protectionist net.

“We are focused on a pragmatic approach and are rapidly negotiating a wider economic agreement with the U.S. to eliminate additional tariffs and to benefit U.K. businesses and our economy,” Jonathan Reynolds, Britain’s trade and industry secretary, said.

Mr. Reynolds added that Britain was not taking any potential action off the table. But Mr. Starmer, who has energetically lobbied Mr. Trump to exempt the country from tariffs, believes that he can ultimately persuade Mr. Trump that Britain’s trade relationship with the United States is balanced.

Britain runs either an $89 billion trade surplus or a $14.5 billion deficit with the United States, depending on whether one cites British or American statistics. The difference rests in part on how the two sides treat offshore financial centers such as Jersey and Guernsey, which are crown dependencies.

“He was working hard, I’ll tell you that,” Mr. Trump said, after Mr. Starmer lobbied him against tariffs at a White House meeting late last month. “He earned whatever the hell they pay him over there.”

Mr. Starmer has also been pushing Mr. Trump to provide American security guarantees to Ukraine as part of a peace negotiation with Russia. The two leaders have spoken regularly by phone since their meeting, as Mr. Starmer has tried to help heal Mr. Trump’s rift with President Volodymyr Zelensky of Ukraine.

But Britain’s decision not to retaliate to the tariffs could complicate Mr. Starmer’s other big priority: to draw his country closer to the European Union after Brexit. The crisis over Ukraine has given the prime minister a chance to collaborate with the European Union on defense and security, and he clearly hopes it could lead to closer trade and economic links.

The divergent responses to the tariffs are a reminder that, in some respects, Britain still faces a choice between the United States and Europe.