President Trump said Thursday he would finalize a trade deal with the U.K. “very soon” as he tries to lock in favorable trade terms for the U.S. despite a court case looming over negotiations.

Mr. Trump said he was “thrilled” that his first trade deal this year was with the United Kingdom. The countries agreed to a deal in principle in May.

“I look forward to finalizing it very soon. We’ll have it done very quickly,” the president said during a joint press conference with British Prime Minister Keir Starmer.

While some countries took a wait-and-see approach or dragged out talks, the U.K. struck an early deal to allow U.S. goods into its markets in exchange for tariff relief and aerospace transactions.

British goods still face Mr. Trump’s blanket 10% levy when they enter the U.S. Still, the deal is expected to lower sector-specific tariffs and a fixed number of British car exports.

The U.K. wants to lower Mr. Trump’s 25% tariffs on steel and aluminum imports. They’d like to slash it to zero, though details are being worked out.

“He’s a tough negotiator. I think it was a better deal for you than us, but these are minor details,” Mr. Trump said of Mr. Starmer.

“It was a very good deal for both of us,” the British prime minister said.

Mr. Trump is shaping his trade agenda with the specter of a Supreme Court case that could strike down one of his main levers for imposing tariffs on other nations.

A series of blue states and small, import-reliant businesses say Mr. Trump overstepped by invoking the International Emergency Economic Powers Act of 1977 to slap “reciprocal” tariffs on dozens of trading partners and drug-trafficking related levies on Canada, Mexico and China.

They secured lower-court victories against Mr. Trump, and the administration appealed to the Supreme Court.

Administration officials say they would have to unwind major trade deals and refund $750 billion to $1 trillion in tariff revenue if the justices strike down Mr. Trump’s powers and the opinion does not arrive until June.

• Tom Howell Jr. can be reached at thowell@washingtontimes.com.