WASHINGTON (Reuters) - President Donald Trump will lay out a more confrontational strategy toward Iran by the United States on Friday in a speech in which he is likely to strike a blow at an international Iran nuclear deal, complicating U.S. relations with European allies.

U.S. President Donald Trump speaks to introduce his Secretary of Homeland Security nominee Kirstjen Nielsen in the East Room of the White House in Washington, U.S., October 12, 2017. REUTERS/Yuri Gripas

U.S. officials said Trump was expected to announce that he will not certify the 2015 Iran nuclear deal, believing the agreement is not in the national interests of the United States. He had certified it twice before but aides said he was reluctant to do so a third time.

Trump could have a last minute change of heart before he outlines his administration’s new approach toward Iran in speech at the White House at 12:45 p.m. EDT (1645 GMT) on Friday.

The step would not withdraw the United States from the deal but would give the U.S. Congress 60 days to decide whether to reimpose the sanctions on Tehran that were suspended under an agreement that was negotiated by the United States and other world powers during the administration of former President Barack Obama.

International inspectors say Iran is in technical compliance with the accord, but Trump says Tehran is in violation of the spirit of the agreement and has done nothing to rein in its ballistic missile program or its financial and military support for Hezbollah and other extremist groups.

White House Chief of Staff John Kelly said the U.S. approach toward Iran is to work with allies in the Middle East to contain Tehran’s activities.

“We have footprints on the ground, naval and Air Force is there to just demonstrate our resolve, our friendship, and try to deter anything that any country out there may do,” Kelly said.

European allies are warning of a split with the United States on the issue.

This week, Trump has heard appeals from British Prime Minister Theresa May and French President Emmanuel Macron for the United States to certify the deal for the sake of allied unity.

“It’s imperative that Europe sticks together on this issue,” German Foreign Minister Sigmar Gabriel told the RND German newspaper group. “We also have to tell the Americans that their behavior on the Iran issue will drive us Europeans into a common position with Russia and China against the USA.”

Signed by the United States, Britain, France, Germany, Russia, China, the European Union and Iran, the deal lifted sanctions on Tehran in exchange for curbs on its nuclear program.

Trump has called the accord “an embarrassment” and “the worst deal ever.”

European officials have categorically ruled out renegotiating the deal, but have said they share Trump’s concerns over Iran’s destabilizing influence in the Middle East.

The threat of new action from Washington has prompted a public display of unity from the rival factions among Iran’s rulers.

CIA Director Mike Pompeo on Thursday kept up a steady drumbeat of Trump administration criticism of Iran, saying Tehran is “mounting a ruthless drive to be the hegemonic power in the region.”

Iran’s intelligence service and the Islamic Revolutionary Guard Corps “are the cudgels of a despotic theocracy, with the IRGC accountable only to a Supreme Leader. They’re the vanguard of a pernicious empire that is expanding its power and influence across the Middle East,” Pompeo said in remarks at the University of Texas in Austin.

In Tampa, Florida, the head of U.S. Central Command said he was concerned about Iran’s long-term activities in the region and he would continue to focus on protecting U.S. troops, even as Iran has said U.S. regional military bases would be at risk if further sanctions were passed.

“Iran is kind of a long-term destabilizing actor in the region and so we remain concerned about their activities as well,” U.S. General Joseph Votel told reporters.