Washington (CNN) Defense Secretary Mark Esper said Tuesday that American troops ordered out of northern Syria will "temporarily" go to Iraq before they return to the US, and that President Donald Trump has not yet approved a plan to keep some troops in Syria to protect oil fields.

"We're conducting a phased withdrawal -- deliberate phased withdrawal from northeast Syria," Esper told CNN's Christiane Amanpour in an exclusive interview held at the Prince Sultan Air Base, located in a desert area east of the Saudi capital of Riyadh. "We will temporarily reposition in Iraq pursuant to bringing the troops home. And so it's just one part of a continuing phase, but eventually those troops are going to come home."

The Iraqi Joint Operations Command said in a statement Tuesday that US troops withdrawing from Syria may enter the Kurdish region of Iraq and then leave the country, but that they do not have permission to remain in Iraq.

The comments come as Esper leads the removal of US troops from northern Syria, where they had been supporting the SDF. After Trump announced the withdrawal of the troops from the region earlier this month, a move that was met with a strong bipartisan rebuke, Turkey began a widely-anticipated offensive there, which eventually slowed after the US brokered a ceasefire between the two countries last week. On Monday, the secretary said some troops will temporarily remain in Syria to protect oil fields in the country as the Pentagon continues to remove other troops from the country.

"Right now, the President has authorized that some would stay in the southern part of Syria," Esper said. "And we're looking maybe keeping some additional forces to ensure that we deny ISIS and others access to these key oil fiends also in middle part of the country, if you will. But that needs to be worked out in time. The President hasn't approved that yet -- I need to take him options sometime here soon."

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