By David Brunnstrom and Hyonhee Shin

WASHINGTON/SEOUL (Reuters) – U.S. President Donald Trump is open to additional talks with Pyongyang over denuclearization, his national security adviser said on Thursday, despite reports that North Korea is reactivating parts of its missile program.

New activity has been detected at a factory that produced North Korea’s first intercontinental ballistic missiles (ICBMs) capable of reaching the United States, South Korea’s JoongAng Ilbo and Donga Ilbo newspapers reported, citing lawmakers briefed by the National Intelligence Service.

This week, two U.S. think tanks and Seoul’s spy agency said North Korea was rebuilding a rocket launch site, prompting Trump to say he would be “very, very disappointed in Chairman Kim” if it were true.

The reports of North Korean activity raise more questions about the future of the dialogue Trump has pursued with North Korean leader Kim Jong Un after a second summit between the two leaders in Vietnam broke down last week.White House national security adviser John Bolton said on Thursday that Trump was still open to additional talks with North Korea over denuclearization.

“The president’s obviously open to talking again. We’ll see when that might be scheduled or how it might work out,” Bolton said in an interview with Fox News.

He said it was too soon to make a determination on the reports of the North Korean activities.

“We have a lot of ways of getting information,” he said. “We’re going to study the situation carefully. As the president said, it would be very, very disappointing if they were taking this direction.”

The Vietnam summit between Kim and Trump last week collapsed over differences on how far North Korea was willing to limit its nuclear program and the degree of U.S. willingness to ease economic sanctions against the isolated country.

Trump, eager for a big foreign policy win on North Korea that has eluded his 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.

MISSILE FACTORY

Movement of cargo vehicles was spotted recently around a North Korean factory at Sanumdong in Pyongyang, which produced ICBMs.

South Korean spy chief Suh Hoon told lawmakers he viewed the activity as missile-related, the JoongAng Ilbo said. It quoted Suh as saying North Korea continued to run its uranium enrichment facility at the main Yongbyon nuclear complex after a first summit between Trump and Kim last June in Singapore.

The Sanumdong factory produced the Hwasong-15 ICBM, which can fly more than 13,000 km (8,080 miles). After its test flight in 2017, North Korea declared the completion of its “state nuclear force,” before pursuing talks with South Korea and the United States last year.

South Korea’s presidential office and defense ministry declined to confirm the reports on Sanumdong, saying they were closely monitoring North Korea’s activities together with the United States.

The U.S. State Department said it could not comment on intelligence matters.

Separately, U.S. think tanks reported on Thursday that North Korea’s Sohae Satellite Launching Station appeared to be operational again after work that began days before Trump met with Kim in Hanoi.

Washington’s Center for Strategic and International Studies think tank called the work a “snapback” after North Korea partially dismantled the site, acting on a pledge by Kim to Trump at the Singapore summit.

“The rebuilding activities at Sohae demonstrate how quickly North Korea can easily render reversible any steps taken towards scrapping its WMD program with little hesitation,” it said.

“North Korea’s actions constitute an affront to the president’s diplomatic strategy (and) demonstrate North Korean pique at Trump’s refusal to lift economic sanctions during the meetings in Hanoi.”

The Washington-based 38 North think tank also said the Sohae site appeared now to have returned to normal operational status.

FILE PHOTO: North Korean leader Kim Jong Un makes his way to board a train to depart for North Korea at Dong Dang railway station in Vietnam, March 2, 2019. REUTERS/Kim Kyung-Hoon

SANCTIONS WARNING

Some analysts see the work as aimed at pressing Washington to agree to a deal, rather than as a definite move to resume tests.

A U.S. government source, who did not want to be identified, said North Korea’s plan in rebuilding the site could have been to offer a demonstration of good faith by conspicuously stopping again if a summit pact was struck, while furnishing a sign of defiance or resolve if the meeting failed.

Imagery from Planet Labs Inc analyzed by the Center for Nonproliferation Studies at the Middlebury Institute of International Studies in California showed activity at Sohae from Feb. 23 until Wednesday.

38 North said photos from Wednesday showed the rail-mounted transfer building used to move rockets at the site was complete, cranes had been removed from the launch pad and the transfer building moved to the end of the pad.

“But we don’t draw any conclusions from that besides they are restoring the facility,” Joel Wit of 38 North told Reuters. “There is no evidence to suggest anything more than that.”

On Wednesday, Bolton, a hardliner who was argued for a tough approach to North Korea in the past, warned of new sanctions if it did not scrap its weapons program.

Despite the sanctions talk, there have been signs across Asia that Trump’s “maximum pressure” sanctions campaign against North Korea has sprung leaks.

In a new sanctions breach, three South Korean companies were found to have brought in more than 13,000 tons of North Korean coal, worth 2.1 billion won ($2 million) since 2017, by making it out to have been produced in China and Vietnam, South Korea said.

North Korean media has given conflicting signals about its relations with the United States, while appearing to target Bolton as a spoiler.

Its state television aired a 78-minute documentary late on Wednesday focused on showing a cordial mood between Trump and Kim as the summit ended, indicating Pyongyang was not about to walk away from negotiations, experts say.

It also showed a stone-faced Bolton during a meeting in Hanoi, while Trump and other U.S. participants were all smiles.

In a return to a more usual, strident tone, the KCNA news agency criticized new small-scale military exercises that the United States and South Korea plan to hold instead of a large-scale spring exercise they have called off.

The news agency said the drills would be a “violent violation” of agreements signed between the United States and North Korea as well as between the two Koreas.

The U.S. and South Korean militaries said last week that they would not carry out a large-scale spring joint military exercises, replacing it with smaller-scale ones.

(Reporting by Jeff Mason and David Brunnstrom; additional reporting by Mark Hosenball, David Alexander and Tim Ahmann in Washington and Hyonhee Shin and Joyce Lee in Seoul; Editing by Clarence Fernandez and Alistair Bell)