President Donald Trump delivered a foreboding message, telling reporters as he posed for photos with senior military leaders that this might be “the calm before the storm”.

The president did not elaborate on what he meant, saying simply, “You’ll find out.”

White House reporters were summoned on Thursday evening and told the president had decided he wanted the press to document a dinner he was holding with the military leaders and their spouses.

Reporters were led hastily to the grand State Dining Room, where they walked into a scene of the president, his highest-ranking military aides and their spouses posing for a group photo. After pictures were taken, the president gestured to the reporters in the room.

Donald TrumpDonald Trump spoke of the ‘calm before the storm’ (Carolyn Kaster/AP)

“You guys know what this represents?” Mr Trump asked. “Maybe it’s the calm before the storm. Could be the calm, the calm before the storm.”

“What storm, Mr. President?” one reporter shouted. ISIS? North Korea? Iran?

Mr Trump would not say. Nor would he clarify the next day during a gathering of manufacturers at the White House, once again teasing that an announcement would be forthcoming down the road.

White House press secretary Sarah Huckabee Sanders also declined to elaborate, saying: “We’re never going to say in advance what the president will do.”

She also denied that Mr Trump was simply being mischievous in an effort to mislead reporters.

During the military dinner, the president praised those assembled for the photo, saying: “We have the world’s great military people in this room, I will tell you that.”

Earlier in the evening, the president had lauded the group, including his defence secretary and chairman of the Joint Chiefs of Staff, and said they would be discussing the most pressing military issues facing the country, including North Korea and Iran.

Mr Trump said “tremendous progress” had been made with respect to the Islamic State group, adding: “I guess the media’s going to be finding out about that over the next short period of time.”

He also denounced Iran, saying the country should not be allowed to obtain nuclear weapons, and offered another stark warning to North Korea’s Kim Jong Un.

“We cannot allow this dictatorship to threaten our nation or allies with unimaginable loss of life,” he said, vowing to “do what we must do to prevent that from happening and it will be done, if necessary”.

He also said that, moving forward, he expects those in the room to provide him with “a broad range of military options, when needed, at a much faster pace.”