Former U.S. professional basketball star Dennis Rodman arrived in North Korea on Tuesday, bringing his “basketball diplomacy” back to the country amid heightened tensions between Washington and Pyongyang over the reclusive nation’s nuclear and missile program and its jailing of four Americans.

“I’m back! I will discuss my mission upon my return to the USA,” Rodman said in a tweet Tuesday, with an attached photo that showed him holding what appeared to be an itinerary for a flight on Air Koryo — the North’s state-owned flagship airline.

Speculation was rife that Rodman would play some unofficial role easing tensions between Washington and Pyongyang, though a top U.S. official visiting Tokyo insisted Rodman’s trip was as a private citizen.

“We are aware of his visit. We wish him well, but we have issued travel warnings to Americans suggested they not travel to North Korea for their own safety,” U.S. Under Secretary of State Thomas Shannon said after talks on the North Korea missile threat with Shotaro Yachi, Japan’s top national security adviser.

In an interesting confluence of timing, Shannon was headed later Tuesday to South Korea, where he was scheduled to hold talks through Thursday.

Contacted by The Japan Times, a State Department spokesperson declined to comment on the record.

However, Daniel Pinkston, a North Korean expert at Troy University in Seoul who advised Rodman on an earlier visit, said his trip was a long time coming.

“He’s had a long-standing invitation, and the North Korean Foreign Ministry communicated that now would be a good time,” Pinkston said.

At Beijing International Airport ahead of his departure, the former NBA bad boy was quoted as saying that he was “just trying to open a door,” and that the issue of the four Americans currently detained in the North was “not my purpose right now.”

Asked whether he had spoken with U.S. President Donald Trump about his trip, Rodman said: “I’m pretty sure he’s pretty much happy with the fact that I’m over here trying to accomplish something that we both need.”

Currently, four Americans are being held in North Korea: Kim Sang Duk and Kim Hak-song, two academics who worked at Pyongyang University of Science and Technology; University of Virginia student Otto Warmbier; and businessman Kim Dong Chul.

Rodman has traveled at least four times to the isolated country and is one of the few Americans to have met North Korean dictator Kim Jong Un. His last trip to the country came in January 2014, when he led a group of former NBA players in an exhibition basketball game said to have been a birthday gift for Kim, who is reportedly a huge fan of the sport.

After his last visit, Rodman faced intense criticism for the trips and for his description of Kim as a “very good guy.” The North Korean leader has been accused of executing scores of officials and others who had defied him, including his uncle and half brother.

The country has also reportedly imprisoned scores of its people in draconian gulags while doling out millions of dollars toward its military programs instead of its impoverished population.

The tattoo- and piercing-covered former basketball player also has a personal relationship with Trump, having appeared on the reality TV show “Celebrity Apprentice,” which was hosted by the president before he was elected.

Trump lauded Rodman for his February 2013 visit to the North, calling him “smart” in an interview with Fox News the following month.

“You look at the world, the world is blowing up around us. Maybe Dennis is a lot better than what we have,” Trump said of Rodman.

“It’s not an act,” he continued, “but he’s a much different guy and this year on the apprentice — it’s amazing how sharp and smart. Dennis is not a stupid guy. He’s smart in many ways, he’s very street wise.”

Rodman also endorsed Trump’s White House drive early in the campaign, in July 2015.

In a video tweeted by Rodman from his Twitter account later Tuesday, his agent Chris Volo noted that the former basketball star was “the only man to have a relationship and be friends” with both Kim and Trump.

Some experts have suggested that the visit may have had at least some level of coordination with the White House.

“Trump praised Rodman’s previous #DPRK trip. Rodman endorsed Trump. High probability of some communication or even coordination,” Suzanne DiMaggio, a director and senior fellow at the New America think tank in Washington, said in a tweet Tuesday.

DiMaggio led a delegation of American experts and at least one U.S. government official for informal talks with North Korean officials in Oslo last month, amid speculation that Washington may be seeking a route to dialogue with Pyongyang.

DPRK is the acronym for the North’s formal name, the Democratic People’s Republic of Korea.

In March, Rodman also alluded to a willingness to act as a kind of special envoy to the North if asked by Trump.

Speaking at a panel discussion on “alternative tools of diplomacy” hosted by West Point’s Modern War Institute, Rodman said: “I’d be there in a heartbeat. Because sports is probably the No. 1 thing on the planet that could actually heal things.”

While there is a precedent for such a scenario — Kenneth Bae, who had been the longest-held U.S. citizen by North Korea, said after he was freed in 2014 that Rodman had been a “catalyst” for his release — some analysts threw cold water on this, noting the flamboyant ex-athlete’s flair for the dramatic and his long-standing invitation to visit Pyongyang.

“I’d be surprised if his trip has any backing from Trump, but then again, you never know with Trump, since he is so unconventional and doesn’t follow normal diplomatic practices,” said Duyeon Kim, a senior fellow with the Korean Peninsula Future Forum think tank in Seoul.

“But I wouldn’t read too much into it yet. It may end up being another show.”

Pyongyang has unleashed a string of missile launches and tests of other advanced weaponry in recent weeks, as it seeks to highlight its progress toward mastering technology needed to mount a nuclear warhead on an intercontinental ballistic missile.

In written testimony to lawmakers ahead of a hearing on the Pentagon budget Monday, U.S. defense chief James Mattis called North Korea “the most urgent and dangerous threat to peace and security” — a dubious distinction that saw it displace Russia as the top threat to the United States.

“Korea’s continued pursuit of nuclear weapons and the means to deliver them has increased in pace and scope,” Mattis said. “The regime’s nuclear weapons program is a clear and present danger to all.”

In a New Year’s Day address, Kim claimed that the North was in the “final stages” of developing an ICBM capable of striking the continental United States. Trump has vowed that a launch of a long-range missile by Pyongyang “won’t happen” on his watch.

North Korea warned Saturday that it was “not too far away” from testing such a missile.

Trump has offered mixed messages on Kim, saying, at various times, that he would be “honored” to meet him under the right conditions and even going so far as to describe him as a “smart cookie.”

But the unpredictable U.S. leader has also described Kim as a “madman with nuclear weapons.”

Information from AFP-JIJI added