While Trump has used the halt in hostilities to declare victory — he called Thursday a "great day for civilization" and proclaimed "millions of lives will be saved" — the cease-fire has cemented Turkey's invasion and seizure of territory while making the U.S. responsible for ensuring Kurdish forces withdraw.

Asked about the situation in Syria at a news conference on Friday, European Council President Donald Tusk said: "This so-called cease-fire is not what we expected. In fact, it's not a cease-fire; it's a demand of capitulation of the Kurds."

After briefing NATO ambassadors in the formal meeting room of the North Atlantic Council, Pompeo appeared at a brief news conference with NATO Secretary-General Jens Stoltenberg, who began by saying: "I welcome that two NATO allies, the United States and Turkey, have agreed on a way forward."

Stoltenberg's remarks hinted at the tensions of recent days, in which Trump first gave the go-ahead for the Turkish offensive and then reversed course amid a storm of criticism. At one point, Trump threatened to "totally destroy and obliterate the economy of Turkey."

Stoltenberg reiterated his carefully calibrated remarks about Turkey. "We all know and understand that the situation in northeast Syria is fragile, difficult," Stoltenberg said. "Turkey is on the front line ... the forefront of a very volatile region. No other ally has suffered more terrorist attacks. They host millions of refugees, and Turkey has legitimate security concerns."

Pompeo reiterated his call for restraint and urged that the efforts by NATO allies to fight the Islamic State not be undermined.

Most experts say many such gains have been put at risk as a result of a hasty U.S. pullout and the Turkish incursion, with hundreds of jihadis reportedly escaping from Kurdish-run detention camps amid the fighting.

At one point on Friday, there seemed to be some disagreement on the Turkish side as to what was agreed — with Turkey saying it was merely a "pause" in its operation — and whether the purported cease-fire was holding, as fighting continued in some areas.

Stoltenberg continued to try to put on a positive spin. "NATO is an important forum for all NATO allies to sit together and address common security concerns, and the situation in northeast Syria is a concern for all NATO allies," he said.

Pompeo, in response to a question, said he could not explain comments by Trump, made in a tweet, declaring the U.S. had secured "the Oil" — saying he had not seen the remarks. It was unclear what oil the president was referring to.

Trump also insisted European allies had agreed to repatriate foreign Islamic State fighters who had been detained in northeast Syria, but Pompeo was more guarded in his remarks and declined to specify which countries might be willing to accept the detainees.

"We have seen comments today from a number of countries who have said they may well be prepared to take back these fighters," Pompeo said. "I have to say I am happy about that. I am disappointed that it didn't occur previously."

Pompeo called on other countries, including European allies, to do more to help Turkey.

"We've seen the burden that that's placed on our NATO ally Turkey, with now some 2 or 3 or 4 million displaced persons inside of Turkey," Pompeo said at the news conference. "That's an enormous burden. Europe needs to provide, to seriously consider how to respond to this threat, this challenge that is presented by migration."