(CNN) When White House aides arrived at work Thursday, they were prepared for a market-shaking event that would prompt jitters among US allies and cause heartburn among establishment thinkers, even Republicans.

They weren't prepared for two such events.

President Donald Trump sent shock waves across the globe when he accepted an invitation from North Korean dictator Kim Jong Un for talks. No sitting US president has ever met with a leader from North Korea. The move represents the largest gamble to date for two truculent leaders who have engaged in a harrowing nuclear stare-down.

It also caught presidential advisers -- who had been hurriedly finalizing details on steel tariffs while also attempting to stave off unsavory questions about a porn actress -- off-guard.

Trump hadn't initially been scheduled to meet with a delegation of South Korea officials in Washington to brief his administration on recent talks with Pyongyang. The group arrived midafternoon as the President was convening sessions with representatives of the video game industry and announcing his new tariffs on imports of steel and aluminum.

But after speaking with the US national security adviser, H.R. McMaster, the group, led by McMaster's South Korean counterpart, Chung Eui-yong, convened in the Oval Office with Trump. The gathering included three US generals -- McMaster, Defense Secretary James Mattis and White House chief of staff John Kelly. It was there, sitting on the gold brocade sofas, that Trump fielded the striking offer from North Korea and readily agreed.

For Trump, the offer and his unprecedented plans to meet the North Korean leader were too great to keep quiet. Trump left the Oval Office intending to return to his private residence. But he made a detour, navigating the corridors of the West Wing toward the press briefing room, a venue he'd yet to speak from during his year-and-a-month as President.

Peeking around a half-opened pocket door, Trump caught the eye of a small handful of reporters and drew them closer to him. First, he asked to speak off the record, but with an ounce of prodding agreed to go on the record, as long as his remarks remained off camera.

"South Korea's going to be making a major statement at about 7 o'clock," Trump said ceremoniously. Vice President Mike Pence stood silently behind him.

"About what?" a puzzled reporter asked.

"The big subject," Trump replied, his scowl turning into a grin.

Thursday, in fact, contained two big subjects at the White House for the government in Seoul: the developments on North Korea and the tariffs on steel, which South Korea exports by millions of tons per year.

Trump clarified.

"North Korea," he said, before ducking back into West Wing.

The brief appearance, which lasted 29 seconds, came amid a sordid swirl of reports about his alleged affair with porn actress Stormy Daniels and a thunderstorm of criticism over his beloved steel tariffs.

It sent reporters and White House officials scrambling. McMaster huddled with press secretary Sarah Sanders in her office to sort out the unusual logistics of a foreign government delivering an announcement from the White House.

It was determined that having Chung deliver his news from the briefing room podium would break protocol and prove confusing. Instead, they sent him outdoors to the set of microphones on permanent standby in the White House driveway.

"President Trump appreciated the briefing and said he would meet Kim Jong Un by May to achieve permanent denuclearization," Chung said.

The decision, which aides said came about quickly in the Oval Office, represents a massive challenge for the President. His aides insist he is up for it.

"President Trump has made his reputation on making deals," one official said. "President Trump was elected in part because he is willing to do -- take approaches very, very different from past approaches and past presidents. That couldn't be better exemplified in his North Korea policy."

Sanders later wrote in a statement that the "place and time" of the meeting were still to be determined. The security and advance work would prove daunting for an experienced White House, let alone an administration still working to find its footing amid persistent chaos and low morale.

The North Korea decision wasn't immune from the appearance of disarray. Speaking in Ethiopia hours before Trump, Secretary of State Rex Tillerson said direct talks between the US and North Korea were still in the distant future.

"We're a long way from negotiations. We just need to be very clear-eyed and realistic about it," Tillerson said. "I don't know yet, until we are able to meet ourselves face to face with representatives of North Korea, whether the conditions are right to even begin thinking about negotiations."

Trump spoke with his top diplomat before his announcement, a senior State Department official said. Both men spoke with Prime Minister Shinzo Abe of Japan, who has expressed deep misgivings about opening talks with North Korea.

Ultimately, the President himself may have been the least surprised at Thursday's developments. He has long remained open to talks with Kim, despite the view of top national security officials that too much is unknown about North Korea's intentions in proposing them.

Trump himself offered the best preview of his move during last Saturday's Gridiron dinner in Washington, a white tie affair for journalists, where few in attendance expected they'd be covering news of an upcoming US-North Korea summit in a matter of days.

"I won't rule out direct talks with Kim Jong Un. I just won't," the President said. "As far as the risk of dealing with a madman is concerned, that's his problem, not mine."