WASHINGTON (Reuters) - U.S. President Donald Trump said on Wednesday he would be very disappointed in North Korean leader Kim Jong Un if reports about rebuilding at a rocket launch site in North Korea were true.

Two U.S. think tanks and South Korea’s Yonhap News Agency reported on Tuesday that work was underway to restore part of North Korea’s Sohae Satellite Launching Station even as Trump met with Kim at a second summit in Hanoi last week.

“I would be very disappointed if that were happening,” Trump told reporters in the Oval Office, when asked if North Korea was breaking a promise.

“Well, we’re going to see. It’s too early to see. ... It’s a very early report. We’re the ones that put it out. But I would be very, very disappointed in Chairman Kim, and I don’t think I will be, but we’ll see what happens. We’ll take a look. It’ll ultimately get solved.”

North Korea began work to dismantle a missile engine test stand at Sohae last year after pledging to do so in a first summit with Trump in June.

A second summit between Trump and Kim broke down last week in Hanoi over differences on how far North Korea was willing to limit its nuclear program and the degree of U.S. willingness to ease sanctions.

“We have a very nasty problem there. We have to solve a problem,” Trump said, while adding in apparent reference to Kim: “The relationship is good.”

Trump, eager for a big foreign policy win on North Korea that has eluded predecessors for decades, has repeatedly stressed his good relationship with Kim. He went as far late last year as saying they “fell in love,” but the bonhomie has failed so far to bridge the wide gap between the two sides.

Satellite images seen by 38 North, a Washington-based North Korea project, showed that structures on the Sohae launch pad had been rebuilt sometime between Feb. 16 and March 2, Jenny Town, managing editor at the project and an analyst at the Stimson Center think tank, told Reuters.

The Sohae Satellite Launching Station launch pad features what researchers of Beyond Parallel, a CSIS project, describe as showing the partially rebuilt rail-mounted rocket transfer structure in a commercial satellite image taken over Tongchang-ri, North Korea on March 2, 2019 and released March 5, 2019. CSIS/Beyond Parallel/DigitalGlobe 2019 via REUTERS.

The Center for Strategic and International Studies think tank released a separate report, also citing satellite imagery, that concluded North Korea was “pursuing a rapid rebuilding” at the site.

News of the work at Sohae was first reported by Yonhap, which quoted South Korea lawmakers on details of a briefing by the country’s National Intelligence Service on Tuesday.

The White House did not immediately respond when asked what Trump meant by “we’re the ones that put it out,” but U.S. and South Korean intelligence agencies cooperate very closely.

A U.S. government source said the work at Sohae likely began before the summit, which was preceded by a series of lower-level talks in February.

SANCTIONS WARNING

Trump’s national security adviser, John Bolton, warned on Tuesday that new sanctions could be introduced if North Korea did not scrap its nuclear weapons program.The breakdown of the Feb. 27-28 summit and Bolton’s sanctions threat have raised questions about the future of the dialogue the Trump administration has pursued in an effort to persuade North Korea to abandon a nuclear weapons program that threatens the United States.

Some analysts have interpreted the work at Sohae as an attempt by North Korea to put pressure on Washington to agree to a deal rather than as a definite move to resume tests there.

The U.S. government source, who did not want to be identified, said North Korea’s plan in rebuilding at the site could have been to conspicuously stop again as a demonstration of good faith if a summit agreement was struck, while the work would represent a sign of defiance or resolve if the meeting failed.

Democrat Ed Markey, ranking member of the Senate East Asia Subcommittee, expressed his concern about the reports, saying that Trump had held Sohae up as evidence that his approach to dealing with Kim was working.

“North Korea’s apparent work at this launch site raises the troubling possibility that yet again Kim Jong Un is more interested in garnering concessions than conducting serious, good faith efforts to denuclearize,” the senator said.

Markey said it was imperative to restart working-level talks with North Korea as soon as possible and added that if Pyongyang were to abandon diplomacy the United States should be ready to consider additional ways to apply pressure.

U.S. Secretary of State Mike Pompeo said on Monday he was hopeful he would send a delegation to North Korea in the coming weeks but that he had “no commitment yet.”

While North Korea’s official media said last week that Kim and Trump had decided at the summit to continue talks, its vice foreign minister, Choe Son Hui, told reporters Kim “might lose his willingness to pursue a deal” and questioned the need to continue.

White House spokeswoman Sarah Sanders said earlier on Wednesday that the United States was “continuing to have ongoing conversations with North Korea,” but did not elaborate.

U.S. Special Representative for North Korea Stephen Biegun, who led pre-summit negotiations, met with his Japanese and South Korean counterparts in Washington on Wednesday to discuss future steps, a State Department official said.