WASHINGTON — The United States has rejected an appeal from Britain, France and Germany to grant broad exemptions to European firms doing business in Iran, saying it would press ahead with sanctions intended to exert “unprecedented” economic pressure on the Tehran regime, U.S. and Western officials told NBC News.

Replying to a June 4 letter from the European powers, Secretary of State Mike Pompeo and Treasury Secretary Steven Mnuchin wrote that the Trump administration would not agree to wide-ranging protections for European companies operating in Iran and instead would grant only limited exceptions based on national security or humanitarian grounds, the officials said.

The stern message comes as the White House has ratcheted up its rhetoric toward Iran, accused Tehran of plotting terrorist attacks in Europe and vowed to hammer the country’s economy.

The letter from the Trump administration marks the latest dispute in an increasingly tense U.S. relationship with European allies, aggravated by the president’s harsh criticism of NATO partners this week during his visit to Brussels.

Having pulled out of the Iran nuclear deal on May 8, the Trump administration plans to reimpose an array of economic sanctions on Iran, including measures designed to cut off Tehran’s financial sector from Western banks. A first wave of sanctions will enter into force by an August deadline, and then another wave will hit in November.

The Iran nuclear deal, which had imposed restrictions on Iran’s nuclear program in return for easing economic sanctions, had “failed to guarantee the safety of the American people,” the letter said, according to U.S. and Western officials.