US Senator: Trump vows to 'destroy' IS before troops leave Syria

A senior Republican senator said on Sunday that President Donald Trump had promised to stay in Syria to finish the job of destroying the Islamic State group - just days after announcing he would be withdrawing troops immediately.

"The president understands the need to finish the job," Lindsay Graham told reporters outside the White House after what he described as a two-hour lunch meeting.

"He told me some things I didn't know that made me feel a lot better about where we're headed in Syria," the South Carolina lawmaker said.

"I think the president is committed to making sure when we leave Syria that ISIS is completely defeated and we are inside the 10-yard line," he said, using an alternative name for the Islamic State group.

When Trump tweeted on December 19 that "we have defeated ISIS in Syria", several military and security experts said he was overstating the case, and warned against a hasty withdrawal.

'Thinking long and hard'

Graham said Trump was "thinking long and hard about Syria and how to withdraw the forces" after ensuring that IS is destroyed, that US-allied Kurdish forces are protected and that "Iran doesn't become the big winner of our leaving".

The senator's remarks after the White House meeting were considerably modulated from his tone earlier in the day, when he told ABC television's "This Week" that "if we leave (Syria) now, the Kurds will get slaughtered".

"I'm going to ask the president to do something that President Obama would never do: reconsider," he said.

Graham said he knew Trump was "frustrated" by his limited options in Syria.

"The president is reconsidering how we would do this," Graham said.

Trump's abrupt decision on Syria stunned regional players, US politicians of both parties and military leaders, who expressed surprise that such a major decision would be announced after apparently so little advance consultation, against the advice of his national security advisors - and on Twitter.

US Defence Secretary Jim Mattis resigned following the announcement, which came on the same day that US officials said Trump was also planning a significant drawdown in Afghanistan, with some reports suggesting as many as half of the 14,000 troops could leave.

Graham warned at the time that a reduction now of US forces in war-torn Afghanistan risked "paving the way toward a second 9/11".

Another prominent critic of the move was retired US army General Stanley McChrystal, the former commander of US and international forces in Afghanistan.

On Sunday, he told ABC that the dual drawdowns could seriously weaken US influence in the region.

"We have a tumultuous regime or region (in Syria) that now has a Russian presence which had been out for about 30 years," he said.

"Iran has increased influence across the region now. If you pull American influence out, you're likely to have greater instability."

Similarly, he said, Trump's planned drawdown in Afghanistan could seriously undercut American leverage there.

"Just when we were starting to sit down with the Taliban, just as we were starting to begin negotiations, he basically traded away the biggest leverage point we have," McChrystal added.