By Elise Labott, Politico–

National security adviser John Bolton left here in frustration Tuesday, with the U.S. and Turkey locked in a political standoff that threatens President Donald Trump’s plans for a troop withdrawal from Syria.

Bolton left Turkey without seeing Turkish President Recep Tayyip Erdogan, who then publicly called earlier comments the top Trump aide had made about Turkey’s role in neighboring Syria a “serious mistake.”

It was a rocky conclusion to Bolton’s overseas trip, which he undertook to explain Trump’s plans for Syria to key U.S. allies. The contretemps also illustrated the risk for Bolton in conducting diplomacy abroad — a role that is not traditionally part of a national security adviser’s portfolio, but one he seems to relish.

On one of several trips abroad he has taken since assuming his job last April, Bolton also found himself casting an eye back home, denouncing media reports suggesting that he and the president were on different pages when it comes to Syria policy.

Bolton, traveling in a U.S. government 757 jet often used by Vice President Mike Pence, left Turkey after Erdogan skipped an anticipated meeting with the Trump adviser and criticized him in a speech to his parliament. The Turkish leader is furious over Bolton’s insistence that U.S. forces would remain in Syria until his country agreed not to attack Kurdish forces in Syria who have fought alongside American troops against the Islamic State.

Bolton had hoped to reach a consensus with Erdogan over a roadmap for a U.S. troop withdrawal which would allow the U.S. to defeat the remnants of the Islamic State, also known as ISIS, while also containing Iran’s military presence in Syria.

But Washington and Ankara are increasingly butting heads over whether and how to protect Syria’s Kurdish fighters after U.S. troops leave.

Little-known to most Americans, the Kurds have fierce defenders among senior national security officials who say they have fought valiantly against ISIS for years. Ensuring their protection has become a major complicating factor in Trump’s desire to exit Syria. Erdogan sees Syria’s Kurdish fighters as indistinguishable from Kurdish insurgents within his country whom he considers terrorists and has threatened to attack them.

John R. Bolton wearing a suit and tie: John Bolton left Turkey without seeing Turkish President Recep Tayyip Erdogan, who publicly called earlier comments the top Trump aide had made about Turkey’s role in neighboring Syria a “serious mistake.”© Nicholas Kamm/AFP/Getty Images John Bolton left Turkey without seeing Turkish President Recep Tayyip Erdogan, who publicly called earlier comments the top Trump aide had made about Turkey’s role in neighboring Syria a “serious mistake.”Despite the sour reception from Erdogan, officials say Bolton’s visit here was worthwhile: He met for more than two hours with his counterpart, Turkish national security adviser Ibrahim Kalin, and the country’s deputy defense and foreign ministers.

According to a U.S. official in that meeting, Bolton presented the Turks with a document listing terms governing the pullout of American forces in a “deliberate, orderly and strong manner.” He also committed to keep some troops at the al-Tanf garrison in southeast Syria near the Jordanian border, which is used to monitor the flow of Iranian arms and forces. And he said the U.S. would help secure the airspace over northeast Syria.

But in language clearly alluding to the long-oppressed Kurds, Bolton added that the United States wanted “the protection of all civilians, particularly local minority populations.”

“The United States opposes any mistreatment of opposition forces who fought with us against ISIS,” the document said.

In Jerusalem on Sunday, Bolton had previewed that tough message, which he planned to deliver directly to Erdogan: President Trump would not pull out the troops until Turkey guaranteed it would not — in the words of Secretary of State Mike Pompeo — “slaughter the Kurds.”

That stance angered Erdogan, who, hours before Bolton’s arrival, published an op-ed in the New York Times insisting his government had “no argument with the Syrian Kurds,” although Ergodan went on to brand Turkey’s Y.P.G. militia as a “terrorist” group that could have no political role in Syria’s future.

Erdogan said that Trump made the right call to withdraw from Syria and proposed a “stabilization force” for Syria, which he said Turkey would stand up and vet. He promised to “cooperate with our actions with our friends and allies.”

But Erdogan also defended his troops’ careful on-the-ground efforts to root out insurgents in Syria, contrasting them to what said were indiscriminate airstrikes against ISIS in Iraq and Syria by the U.S.-backed coalition with no regard for civilian casualties. During a meeting with Kalin, his counterpart, Bolton said that he found the editorial “wrong and offensive,” according to the U.S. official in the meeting.

Erdogan did call into that meeting, only to say he was unable to attend because he had to give a speech to members of his party in parliament — a speech in which he attacked Bolton for his comments in Jerusalem, calling them a “serious mistake” by casting doubt on Turkey’s intentions.

“Those who cast aspersions on Turkey that claiming it will massacre the Kurds in Syria are actually well aware of the fact behind the issue,” Erdogan said. He said that preparations were almost complete for operations against “terrorist groups” in Syria, seemingly an ominous sign of an offensive against the Kurds. (Kalin told Bolton, however, that Erdogan has committed not to launch such an offensive action while U.S. forces are still in Syria.)

“The Turks stuck by their position that the P.Y.D. and the Y.P.G. are terrorist groups and they’re free to go after them,” the U.S. official said, using two interchangeable acronyms for the Kurdish group.

The question now is whether President Trump will stick by his promise to protect the Kurds against Turkey, even if it means suspending the departure of US troops.

The evolving timeframe for the pullout of U..S forces has added to the confusion surrounding the US policy toward Syria.

Trump’s initial vow on December 19 to bring U.S. troops home “now “ — which followed a phone call with Erdogan, who had asked Trump why American forces remained in the country — quickly softened after advisers voiced concern a swift exit was unfeasible and unwise and could put the Kurds in danger.

Days later, after another call with Erdogan, Trump promised a “slow” and “highly coordinated pullout” of troops.

“He thought he got a commitment from Erdogan that he would protect them,” a senior administration official said about the Dec. 23 call between the two men

U.S. officials say Trump was further persuaded by military commanders during his post-Christmas visit to al-Assad airbase in Iraq that slowing the withdrawal could enable the US to meet its goals of defeating the remnants of ISIS, containing and Iran and protecting the Kurds.

Bolton’s visit to Turkey, a NATO ally, was arguably the most critical of an overlapping region-wide tour by Bolton and Secretary of State Mike Pompeo, who arrived in Jordan Tuesday, aimed at containing the fallout over President Trump’s abrupt announcement — against the advice of many senior officials — that U.S. troops would exit Syria “now.”

While traveling, he bristled at media reports saying that he was walking back Trump’s declaration of a rapid U.S. exit from Syria.

Both Bolton and Pompeo said this week there is “no timeline” for the withdrawal, while insisting the policy remained unchanged. That reflected the Trump administration’s competing objectives: assuring nervous allies that the U.S. was not leaving Syria hastily while also satisfying an impatient president’s desire to bring troops back home.

Trump himself also pushed back on media reports about the dueling narratives. In a tweet Monday, Trump wrote “The Failing New York Times has knowingly written a very inaccurate story on my intentions on Syria. No different from my original statements, we will be leaving at a proper pace while at the same time continuing to fight ISIS and doing all else that is prudent and necessary.”

“My thoughts exactly,” Bolton replied in a tweet of his own.