SEOUL (BLOOMBERG) - North Korean leader Kim Jong Un is showing signs he might fire his first rocket in 15 months. Long-time observers suspect he is bluffing.

Two days after Mr Kim's summit with US President Donald Trump broke down over sanctions relief and disarmament steps last month, satellite images showed that North Korea was rebuilding a long-range rocket site it recently dismantled.

The activity suggests that the country could be preparing to launch a missile or satellite that would push back against Mr Trump while providing valuable data to improve his weapons capability.

"It is a big gamble," said Dr Jenny Town, managing editor for the North Korea-focused 38 North website. "If North Korea does launch a satellite, it could derail all of North Korea's diplomatic goodwill built up over the past year."

Besides potentially angering Mr Trump, North Korea must avoid undercutting support for sanctions relief from China and Russia.

Both nations, which wield vetoes on the United Nations Security Council, approved the penalties after the country tested nuclear bombs and ballistic missiles in defiance of international prohibitions.

Any launch would be the first since Mr Kim fired off an intercontinental ballistic missile in November 2017 capable of reaching any US city and declared his weapons programme complete.

Just prepping a potential launch site sends a pointed message to Mr Trump, who has repeatedly cited Mr Kim's decision to refrain from weapons tests to justify his controversial decision to engage the North Korean leader one on one.

'PERMANENTLY STOP'

North Korean Foreign Minister Ri Yong Ho told a rare news conference after the Hanoi talks that Mr Kim had pledged to not to restart testing.

"During this summit, we expressed intent to give commitment in a paper form that we permanently stop nuclear tests and test-launch of long-range rockets, to ease the US concerns," Mr Ri said on March 1.

Images released last week by Beyond Parallel - part of the Washington-based Centre for Strategic and International Studies - showed that North Korea was rebuilding a long-range rocket site at the Sohae Launch Facility.

The site was dismantled in an apparent show of goodwill after Mr Trump's first summit with Mr Kim in June and the US President said he would be "very disappointed" if it was being rebuilt.

SPY SATELLITES

A separate report showed increased activity just before the February summit at a rocket production facility called Sanumdong in the Pyongyang area, where long-range missiles and space launch vehicles are constructed.

Dr Town, who's also a research fellow at the Washington-based Stimson Centre, said it was too early to say what North Korea was doing based only on satellite imagery.

The regime might be preparing an actual launch or going through the motions to increase its leverage, knowing that what it does is watched by US spy satellites, she said.

US National Security Adviser John Bolton declined to speculate about Mr Kim's intentions when asked about the reports on Sunday.

The State Department's special representative for North Korea, Mr Stephen Biegun, also expressed caution and lamented analysts' apparent willingness to assign too much meaning to the imagery.

"We don't know if it's intended to send any particular statement to us," Mr Biegun said on Monday at the Carnegie Endowment for International Peace.

"It continues to boggle my mind how quickly so many are pressing to reach conclusions about all this."

Instead of a missile test, North Korea might say it was launching a rocket to deliver a satellite into space. The country has taken such steps previously, arguing it was within its sovereign rights to operate a space programme.

North Korea also appears to have stepped up activity at a facility suspected of enriching uranium for weapons, South Korean TV network KBS reported late on Monday, citing unidentified intelligence sources.

SIMILAR TECHNOLOGY

The latest UN resolution punishing the regime for its 2017 ballistic missile test called for the suspension of any launches using ballistic missile technology.

That means even a civilian satellite launch would be a violation, said Mr Oh Joon, a former South Korean ambassador to the UN.

"China and Russia won't be able to say that North Korea has been abiding by the resolutions and sanctions should be eased," Mr Oh said.

A space launch could provide North Korea's missile programme a chance to test ICBM engines and guidance systems, said Dr Jeffrey Lewis, director of the East Asia Non-proliferation Programme at the Middlebury Institute of International Studies in Monterey, California.

"The technology for making sure you put the satellite into the right orbit is the same technology for making sure the missile is on the right course," Dr Lewis said, noting that previous North Korean space launches used older technology. "There is also the possibility that they will take one of these new missiles, paint it white and put a space logo on it."

Mr Kim could also be prepping the launch facilities to increase their value in future talks with the US, said Dr Go Myong-Hyun, a research fellow at Asan Institute for Policy Studies in Seoul.

North Korea's offer to close parts of its main nuclear research facility in Yongbyon in return for sanctions relief didn't satisfy Mr Trump in Hanoi.

"It is trying to change the view within the US administration and outside that what North Korea's offered was not good enough," Dr Go said. "North Korea's message is that doing a deal with it and easing sanctions are the best way to stop its provocations."