Washington (CNN) President Donald Trump announced his intent to nominate Mark Esper to be secretary of defense on Friday, the White House said.

Trump tapped Esper earlier this week to take the helm of the Pentagon in an acting capacity after announcing acting Defense Secretary Patrick Shanahan's plans to step down. Esper was slated to take over as acting secretary on Sunday, but due to federal rules he will need to step down from that position to go through the formal confirmation process.

Trump was expected to nominate Esper , two sources close to the White House had told CNN earlier Friday. Esper had begun filling out paperwork for his nomination and the President in the last day had been calling supporters to build support for Esper's forthcoming nomination, one person close to the White House said.

Trump's announced intent means it is likely the Pentagon will go through several leadership changes in the coming weeks, at a time when the US is confronting one of the most precarious national security situations of Trump's presidency -- tensions with Iran

Shanahan is scheduled to step down from his acting post on Sunday, just days after Trump nearly launched military strikes on three Iranian targets before calling the attack off minutes before it was to be launched.

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