Sen. Lindsey Graham, R-S.C., who has been a vocal critic of President Trump’s decision to move U.S. troops out of Syria, said on Sunday that he is now “increasingly optimistic that we can have some historic solutions” there.

Speaking on “Sunday Morning Futures” with Maria Bartiromo, Graham, the chairman of the Senate Judiciary Committee, said he spoke with Trump on Saturday night about the objectives in Syria and was encouraged by their discussion over the fight against Islamic State terrorists.

“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 told Bartiromo on Sunday.

He went on to explain what the president told him over the weekend and outlined the objectives:

“To make sure we have a demilitarized zone between Turkey and the Kurds,” Graham said. “The Kurds were the allies who helped us defeat ISIS. They lost 10,000 soldiers, we’ve lost eight in four years, God bless the eight, but it was the Kurds who did most of the fighting.”

“Protect our NATO ally Turkey from elements of the Kurds that they consider to be terrorists. A demilitarized zone occupied by international forces, no Americans, but we provide airpower,” he continued.

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Also Sunday, Secretary of State Mike Pompeo defended the White House’s decision to withdraw U.S. troops from northern Syrian ahead of Turkey’s invasion of the region, as well as the planned five-day cease-fire between the Kurds and Turkey that he and Vice President Pence helped negotiate late last week, following a meeting with Turkish President Recep Tayyip Erdoğan in Ankara.

The deal is for a 120-hour cease-fire, during which time the Kurdish-led forces could pull back from the roughly 20-mile-wide safe zone on the Turkish-Syrian border. All Turkish military operations under the recent offensive known as Operation Peace Spring are to pause during that time, and the operation itself will come to an end entirely upon the completion of the Kurdish withdrawal, under the terms of the deal.

Trump ordered the bulk of the approximately 1,000 U.S. troops in Syria to withdraw after officials said Erdoğan made it clear in a phone call that his forces were about to invade Syria to push back Kurdish forces, which Turkey has considered to be terrorists.

Between 200 and 300 U.S. troops are to remain at the southern Syrian outpost of Al-Tanf.

Last week, Trump sent a letter to Erdoğan encouraging him to “work out a good deal,” threatening to “destroy” the Turkish economy if he continued his aggression against the Kurds.

“The president appreciates what the Kurds have done,” Graham told Bartiromo on Sunday. “He wants to make sure ISIS does not come back. I expect we will continue to partner with the Kurds in eastern Syria to make sure ISIS does not reemerge. That is in our national security interest and we owe it to the Kurds.”

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Graham also said Trump has been “thinking outside the box” about securing oil.

“Not only are we going to deny the oil fields falling into Iranian hands, I believe we are on the verge of a joint venture between us and the Syrian democratic forces that helped destroy ISIS and keep them destroyed to modernize the oil fields and make sure they get the revenue, not the Iranians, not Assad, and it can help pay for our small commitment in the future,” Graham said. “And, protecting Israel is the number one objective. We can do all of that with a very small force. I’m increasingly optimistic. This can turn out very well.”

Bartiromo then pointed out that earlier this month Graham had been a staunch critic of the president’s move to pull the troops out of Syria.

“I still believe that if we abandon the Kurds, nobody helps you in the future,” Graham said in response. “They’ve lost 10,000 fighters to destroy the caliphate, but there are 15 or 20,000 ISIS fighters roaming around in Syria and Iraq. A small contingent of Americans providing air power and capability will keep ISIS at bay and keep the jails locked up and the ISIS fighters won’t break out.”

He went on to say, “What I heard from the president was... 'play the ball as you lie,' [which] is a concept in golf. After Erdoğan’s invasion, things have gotten scrambled in Syria, but I see a way forward now that really, quite frankly, is historic.”

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Graham continued, “Historic security for Turkey, historic security for the Kurds, a plan to keep ISIS down and out forever, and the chance to keep the oil fields in the hands of our allies, not enemies, would be a hell of an outcome, and I think that’s now possible.”

Fox Business Network's Maria Bartiromo contributed to this report.