New secretary of state Mike Pompeo said Friday that he believes North Korea is serious about denuclearizing, but he warned that without a substantial “fix” to the Iran nuclear deal, President Trump is likely to walk away from it.

In his first news conference since being sworn in Thursday, Pompeo repeatedly invoked Trump’s name as he fielded questions at the end of a day filled with meetings at NATO headquarters.

Pompeo, who made a secret trip to Pyongyang over Easter, said he came away with a “sense” that Kim Jong Un is willing to denuclearize.

“The economic pressure that has been put in place by this global effort that President Trump led has led him to believe that it’s in his best interest to come to the table and talk about denuclearization,” he said. “I’m always careful. There’s a lot of history here, where promises have been made, hopes have been raised and then dashed.”

Pompeo sounded a less optimistic note about the fate of the 2015 Iran nuclear deal negotiated with the United States and five other world powers, although he said no decision has been made yet.

“Absent a substantial fix, absent overcoming the shortcomings, the flaws of the deal, [the United States] is unlikely to stay in that deal,” he said.

Pompeo leaves Saturday for a trip to Saudi Arabia, Israel and Jordan, three countries where he said the Iran deal will be discussed. He returns Monday to Washington to lead the State Department at a time when many employees have felt their role in foreign policy has been marginalized. Pompeo said he aims to bring their “swagger” back.

“We will be out doing the things that they came on board at the State Department to do,” he said. “To be professional, to deliver diplomacy, American diplomacy, around the world. That’s my mission — to build that esprit and get the team on the field so that we can effectuate diplomacy.”

In a sign of the rank and file’s eagerness to return to the center of U.S. foreign policy, the State Department website slipped into a rare expression of bureaucratic glee, displaying his photograph and the caption “Welcome Mike Pompeo! 70th U.S. Secretary of State.”

His stamina is unlikely to disappoint. Pompeo showed no signs of fatigue at the end of a workday that ended halfway around the world and 24 hours after he was sworn into office.

The unspoken message that Pompeo projected is that he is not like his predecessor, Rex Tillerson.

Several NATO diplomats praised Pompeo’s decision to go directly from his swearing-in ceremony to the airport to attend Friday’s meeting at NATO, an alliance that in the past Trump has criticized as obsolete.

“The work that’s being done here today is invaluable, and our objectives are important, and this mission means a lot to the United States of America,” Pompeo said. “The president very much wanted me to get here, and I’m glad we were able to make it.”

The gesture did not pass unnoticed.

“He actually jumped on the plane just after he was sworn in,” NATO Secretary General Jens Stoltenberg told reporters, with some wonder in his voice as he pinpointed the exact moment when Pompeo sat down with his fellow diplomats for a working breakfast — 12 hours and 34 minutes after the ceremony. “I think that’s actually a new record. And it also shows his strong personal commitment to the alliance, and it reaffirms the commitment of the United States and President Trump to the transatlantic bond.”

A senior NATO diplomat favorably compared Pompeo’s blitz-speed trip with Tillerson’s stuttering start with the alliance. Tillerson forced the 28 other foreign ministers to make a last-minute change to their schedules so that he would not visit Moscow before talking to his fellow NATO diplomats.

“The fact that a NATO foreign ministers meeting is his number one event to attend, and there were not any people that were acting on his behalf, but he was coming by himself, that’s quite a message,” the diplomat said, speaking on the condition of anonymity to compare the two U.S. officials.

NATO diplomats who felt Tillerson was dismissive toward them said they appreciated Pompeo’s approach.

They said Pompeo referred to his Cold War-era military service in Europe in his opening remarks to his fellow ministers. Although Tillerson was often tough on the Kremlin in NATO meetings, the diplomats were aware he had once received an award from Russian President Vladimir Putin in his previous role as ExxonMobil’s chief executive.

There was no shortage of pressing issues to talk about — more than a one-day meeting can accommodate — including Russia’s attempts to interfere in democracies and the efforts to jump-start peace talks on Syria. There was a consensus that Russian aggression needs to be countered, including mounting a better defense against cyberattacks.

“President Trump has made it very clear,” Pompeo told reporters. “The choice is up to Vladimir Putin and the Russians. We would love nothing more for them to rejoin the democratic world and behave in ways that they’re not doing today. We’re very much prepared to have that dialogue. It’s their choice if they want to be part of that or not.”

But in the end, the highlight of the meeting for many of the foreign ministers was the chance to assess Pompeo and his relationship with Trump.

While most of the senior diplomats liked and respected Tillerson, they often said they did not know whether he reflected Trump’s positions or whether he had much influence on U.S. foreign policy.

Pompeo’s arrival seemed to herald a new era.

Quentin Ariès in Brussels contributed to this report.