British aircraft parts will be exempted from U.S. import duties as part of a growing trade deal with the Donald Trump administration.

U.S. Commerce Secretary Howard Lutnick said engines with Rolls-Royce and similar aircraft parts will be able to enter the U.S. market without tariffs, as part of a trade agreement announced last week with the UK.

However, in the five-page document released on Thursday in the transaction announcement, no mention of the exemption, listing the terms of the "Economic Boom Agreement", and the final details will still be eliminated.

UK business secretary Jonathan Reynolds told the Sunday Times that the broader aerospace industry would have a “specific zero-tax guarantee” in the agreement.

Such a deal would provide certainty for a £40 billion industry that offers 450,000 jobs in the UK.

This deal is also important to the United States. Boeing imports of Rolls-Royce engines for its commercial passenger planes and repair and maintenance facilities in the United States also require regular flow.

Lutnick said on Thursday that a British company that wanted to be named would buy a $10 billion (£7.5 billion) Boeing aircraft. On Friday, British Airways boss IAG confirmed it was buying the plane.

The auto and steel industry has high hopes for aerospace deals after relief to the automotive and steel industry, which has provided relief to the automotive and steel industry due to fears of unemployment.

While some of these terms are unclear, the deal could reduce the auto tariffs on at least 100,000 vehicles per year from 27.5% to 10%, while steel tariffs are reduced to zero.

British ambassador to the United States Peter Mandelson said the agreement on UK car exports immediately prevented unemployment at Jaguar Land Rover plants in the West Midlands.

Renault and Prime Minister Keir Starmer both said the UK also hopes to increase the quota for UK-made cars to the initial 100,000 as part of the final agreement as it threatens to act as an export cap.

The deal hopes to be an aviation agreement after the U.S. began an investigation into whether imported aircraft, jet engines and parts represent national security threats on May 1.

Its risk of “concentration of U.S. imports” for a few suppliers and the risk of “impacts of foreign government subsidies and predatory trade practices” is expected to pave the way for higher tariffs.

But the aerospace and aviation industry has been lobbying the White House to preserve a 45-year-old treaty that allows aircraft and parts to largely be on duty across borders.

The Ministry of Commerce and Trade has been contacted for comment.