Washington — President Trump didn't let intense Republican criticism of his decision to withdraw troops from northern Syria rattle him Monday, insisting he made the right call in deciding to leave the unstable region to Turkey and other actors.

Experts and the president's own allies like Senator Lindsey Graham fear the decision to withdraw from the region will endanger Kurdish allies there, with Turkey threatening to overwhelm them. Mr. Trump, asked why he's siding with authoritarian Turkish President Recep Tayyip Erdogan over Kurdish allies, insisted he's not siding with anyone and is adhering to his campaign promise of "America first."

"I'm not siding with anybody. We've been in Syria for many years. You know, Syria was supposed to be a short-term hit," the president said in the Roosevelt Room, where he signed two trade agreements with Japan.

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The president said he's leaving the region in the hands of Turkey, Russia, Iran, Iraq and Syria — which is exactly what allies fear. Mr. Trump explained that he campaigned on pulling the U.S. out of needless wars in the Middle East, and noted the worst part of his job is writing to families of American soldiers who died.

"It's the hardest thing I have to do in this job. I hate it. I hate it," Mr. Trump said.

The president insisted he's polling well in the 2020 presidential race and bashed Democratic House Intelligence Chairman Adam Schiff for moving forward with an impeachment inquiry. The inquiry, sparked by a whistleblower complaint about the president's call with Ukraine's president in which he asked for an investigation into the Bidens, has occupied much of the president's attention in the last week and a half.