President Trump will only withdraw American troops from northern Syria if the Turkish government guarantees it won't attack US-backed Syrian Kurdish forces, according to national security adviser John Bolton on Sunday.

According to NBC News, Trump demanded the commitment from Turkish President Recep Tayyip Erdogan as one of several conditions which need to be met before US forces mostly exit the region.

"There are objectives that we want to accomplish that condition the withdrawal," said Bolton.

He spoke to reporters traveling with him to Israel and Turkey as he tried to clarify Trump’s Syria withdrawal policy for allies. He’s meeting with Israeli officials Sunday and Monday, and with Turkish officials, including Erdogan, on Tuesday. Since Trump abruptly announced on Dec. 19 that all U.S. forces in Syria would exit immediately, administration officials have shifted the timing to say it would happen more slowly. Officials are now setting a series of conditions for withdrawal that must first be met, which Bolton described as “policy decisions that we need to implement.” -NBC News

"This is a cause and effect mission," said Bolton. "Timetables or the timing of the withdrawal occurs as a result of the fulfillment of the conditions and the establishment of the circumstances that we want to see. And once that’s done, then you talk about a timetable."

Bolton also noted that the US troop withdrawal will not be a complete exit from Syria as Trump had originally ordered. Instead, most of the American forces would be withdrawn from northern Syria - where the majority of an estimated 2,000 US troops are deployed, while a small number of troops would remain in the southern part of the country.

"The primary point is we are going to withdraw from northeastern Syria," said Bolton.

"So it’s going to be a different environment after we leave, there is no question about that," he added. "But there is no desire to see Iran’s influence spread that’s for sure."

In regards to the Al Tanf garrison where a few hundred troops are deployed, Bolton suggested that it was "still very strategically important in connection with our determination that Iran not achieve this arc of control stretching from Iran through Iraq into Lebanon and into Syria."

Al Tanf started out as a base to train fighters against ISIS but has morphed into playing a critical role in the U.S. effort to diminish Iran's influence in the region. It’s unclear what the U.S.’s legal justification would be for maintaining troops there, although Bolton cited Article II of the Constitution, which names the president the Commander-in-Chief of the country's armed forces. “I think there’s plenty of legal justification about concern for the resurgence of ISIS,” he said. “But I’m a strong believer in Article II, and I think that what that means is the president has full authority to protect American and allied interests anywhere around the world.” -NBC News

Bolton will be discussing Iran during his meetings in Israel, where Trump's Syria withdrawal announcement was greeted with Dismay.

"I will discuss with his people efforts to stop the Iranian aggression in our region, the situation in Syria — following President Trump's decision," said Israeli Prime Minister Benjamin Netanyahu at the start of a Cabinet meeting Sunday. "Our position is clear — we continue to act against the Iranian military buildup in Syria, including these days, and we are acting against anyone who undermines or tries to undermine Israel's security."

While in Turkey, Bolton will face off with Erdogan - who considers the Kurdish forces in Syria to be terrorists which endanger Turkey. Bolton has already warned Turkey against further military action against Syrian Kurds without US consent.

"We don't think the Turks ought to undertake military action that's not fully coordinated with and agreed to by the United States, at a minimum so they don't endanger our troops, but also so that they meet the president’s requirement that the Syrian opposition forces that have fought with us are not endangered," said Bolton, adding that the US has "told the Kurds our best judgment is that you stand fast now."