Republican Sen. Lindsey Graham, who has been one of the most vocal critics of President Donald Trump's decision to move U.S. troops out of northeastern Syria, said on Sunday he now believed "historic solutions" were possible.

In an interview with Fox News Channel, Graham said a conversation he had with Trump over the weekend had fueled his optimism that a solution could be reached where the security of Turkey and the Kurds was guaranteed and fighters from Islamic State contained.

"I am increasingly optimistic that we can have some historic solutions in Syria that have eluded us for years if we play our cards right," Graham said.