But Tillerson reassured his audience that they would be consulted on plans to restructure the department even as they work together on the key challenges.

North Korea’s efforts to develop an arsenal of nuclear-armed missiles capable of reaching US cities were the “greatest threat” faced by the United States, he said.

Tillerson told the diplomats that he had advised Trump to “test” China’s commitment to reining in its neighbour by “leaning in hard” on Preident Xi.

If Beijing failed to enforce existing UN sanctions, he warned, then Washington could take action against Chinese banks or companies that deal with Pyongyang.

“So it’s a pressure campaign that has a knob on it. I’d say we’re at about dial setting 5 or 6 right now,” he said, without saying how high the dial goes.

“I would say we’re at about the 20 to 25 per cent stage of this strategy... but we’ve got a lot of work left to do to keep that pressure on.”

China’s role in North Korea may be the most pressing issue, but Tillerson said he sensed an opening to reset the basis of China-US ties for the next 50 years.

Trump and Xi, the leaders of the world’s two biggest powers, met last month in Florida and Tillerson said he wanted the bilateral dialogue to intensify.

Differences remain over freedom of navigation in waters claimed by China in the South China Sea and the trans-Pacific trade imbalance.

But Tillerson said ties were at a “point of inflection” and ripe for review.

“Let’s kind of revisit this relationship, and what is it going to be over the next half century.

“I think it’s a tremendous opportunity we have to define that, and there seems to be a great interest on the part of the Chinese leadership to do that as well.”

Before North Korea’s latest weapons tests, Trump had made the battle to eradicate “radical Islamic terrorism the focus of his foreign policy.

It remains a key goal, and Tillerson said the State Department would be part of the effort.

He described the threat as emanating in “concentric circles” from the battlefields of Iraq and Syria through the Middle East to Africa and Central Asia.

“So a lot of work ahead of us,” he said, underlining that the battle is central to policy in the region.

“Many of you are directly engaged in it already. Many more of you are going to become engaged in it, I think you can expect.”

In his former job as CEO of energy giant ExxonMobil, Tillerson was a frequent visitor to Russia pursuing oil deals with President Vladimir Putin’s Kremlin.

Russia clearly hoped that Trump’s election victory and Tillerson’s appointment would lead to warmer ties with Washington - that has not happened.

Tillerson told his colleagues that, on a visit to Moscow last month, he had told Putin that relations are as bad as they have been since the Cold War.

“He did not disagree. He shrugged his shoulders and nodded in agreement,” Tillerson said.

Washington hopes to work with Russia to develop ceasefire zones in Syria, but the former foes are still divided over Russia’s intervention in Ukraine.

So the secretary, who meets Russia’s Foreign Minister Sergei Lavrov in Alaska next week, said he would work on “some small things” to build a level of trust.

“So that’s what we’re hoping, is that we can begin to build a way in which we can learn how to work with one another. I don’t know whether we can or not,” he said.

Tillerson cited work in Africa to alleviate health crises and disrupt terror networks, and in Latin America to combat trafficking and extremist finance.

But his list of priorities included no reference to Europe, beyond repeating Trump’s call for Nato members to spend more on collective defence.