MATTHEW PENNINGTON
Associated Press

WASHINGTON (AP) — North Korea is upgrading its main rocket launch site and has conducted a series of engine tests as it develops a mobile, intercontinental missile that could increase the threat it poses to the United States, a U.S. research institute said Tuesday.

The findings are based on satellite photos of the west coast site of Sohae, analyzed by the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies.

North Korea blasted a rocket into space from site a year-and-half-ago, and the photos indicate it has made significant, recent progress upgrading facilities at Sohae to handle bigger rockets. A launch tower has been expanded to handle rockets 20 meters higher than the 30-meter-long Unha-3 that blasted off in December 2012.

The flurry of activity comes as North Korea has been test-firing short-range missiles from elsewhere, drawing U.N. Security Council condemnation July 15. The North fired another short-range missile into waters off its east coast on Saturday.

Adm. Samuel Locklear, commander of U.S. forces in the Pacific, told reporters Tuesday he believes North Korea has continued to make “steady progress” in both its missile technology and nuclear capability. He said he has to “plan for the worst” of what North Korea says it has or demonstrates it might have.

A major construction program has been underway at Sohae since mid-2013, according the institute, which is publishing the findings on its website, 38 North. North Korea says the Unha-3 was part of a peaceful space program, but the U.S. is concerned it puts the North closer to its goal of having a nuclear-tipped missile that can reach America.

In addition to the higher launch tower, a new wider road has been completed at Sohae that could carry larger rockets to the launch pad, and an existing rail line is being built that could also perform that function by next year, 38 North says.

Perhaps of greatest concern to the U.S. are the indications Pyongyang recently conducted its fourth test this year of an engine that could be used for a mobile intercontinental missile known as the KN-08.

38 North says what appears to be the engine of the main section of the KN-08 was tested between mid-June and early July at Sohae. If this year’s series of engine tests have gone well — still an unknown — that stage of the missile’s development may wind down by year’s end, paving the way for test flights, it says.

In January, Director of National Intelligence James Clapper told a congressional hearing that North Korea had taken initial steps toward fielding the KN-08 although it remains untested.

Assessing the intentions of North Korea’s secretive government and the nation’s technical capabilities is notoriously difficult. A mobile missile is potentially more threatening as it could be deployed more quickly and discreetly.

Experts say North Korea has probably not yet managed to miniaturize a nuclear device that it could mount on a long-range missile capable of hitting mainland America. Pyongyang has not conducted a nuclear test explosion since February 2013 despite speculation it was preparing to do so this spring. Such a test could help hone its capabilities.

Secretary of State John Kerry said last week that North Korea has been “quieter” than in the past, which he attributed to U.S. efforts to engage with Pyongyang’s only ally, China.

But in a sign of concern, the House on Monday passed a bill to toughen sanctions and restrict North Korea’s access to hard currency. The bill would empower President Barack Obama to target foreign banks that facilitate the North’s development and proliferation of weapons technology by barring them from the U.S. financial system.

Prospects for the legislation’s passage through the Senate are uncertain.

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