New satellite images indicate that major construction work is underway at North Korea’s missile launch station, a U.S. think tank said Tuesday, while the U.S. and China discussed resuming multinational talks to denuclearize the communist state.

In its analysis of commercial aerial photos taken Oct. 9, the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies said that a second flat mobile missile launch pad may be under development in the western town of Dongchang, where the North successfully fired a long-range rocket in December. The researchers projected the work could be completed by mid-2014.

Also possibly under construction are two new bridges and a new road linking the area with the missile assembly building and Sohae railroad, it added. The existing Unha launch pad is apparently being upgraded to facilitate future tests of larger space launch vehicles.

“While it is too soon to reach a definitive judgment, evidence is growing that these activities are intended to support the two main priorities for North Korea’s rocket program ― launches of larger rockets and of new mobile missiles,” the Washington-based think tank said on its website, 38 North.

“The new road has been strengthened and widened for use by heavy vehicles, possibly including transporter-erector-launchers for mobile missiles.”

The analysis is the latest in a recent string of findings that pointed to potential developments of Pyongyang’s nuclear program.

SAIS and Seoul officials have also said that the rogue regime of Kim Jong-un had restarted a 5-megawatt reactor capable of generating plutonium for weapons, which could be used as another bargaining chip in its future nuclear negotiations with Washington.

The fresh evidence emerged as China is ramping up efforts to revive the six-party talks after a five-year hiatus while South Korea and the U.S. are seen to remain firm in their demands that the North show clear commitment to denuclearization before they reopen negotiations.

Wu Dawei, China’s chief nuclear envoy and special representative for Korean Peninsula affairs, met in Washington on Monday with his U.S. counterpart Glyn Davies, special representative for North Korea policy, and Daniel Russel, assistant secretary for East Asian and Pacific affairs at the State Department.

The two sides had “a productive set of discussions” on “how to achieve our shared goal of a denuclearized North Korea in a peaceful manner,” the State Department said in a statement.

Starting next week, Cho Tae-yong, Seoul’s special representative for Korean Peninsula peace and security affairs, will also travel to Washington and Beijing for separate talks with Davies and Wu.

After a months-long salvo of war threats, the North, with strong backing from China, has been calling for unconditional, high-level dialogue with the U.S. and a resumption of the six-party talks also involving Japan and Russia.

During recent meetings with former U.S. administration officials and scholars in London and Beijing, Pyongyang officials including Vice Foreign Ministers Kim Kye-gwan and Ri Yong-ho stressed the regime’s focus on the economy and displayed its readiness to return to the negotiating table.

But Seoul and Washington have rejected “talks for talks’ sake,” demanding irrevocable pledges for denuclearization to prove its sincerity.

“We’re open to dialogue, but at the same time, we stick to our position that the dialogue should be one that can achieve substantive progress on the denuclearization front,” Foreign Ministry spokesman Cho Tai-young told reporters.

“In this regard, South Korea and the U.S. are discussing with key stakeholders such as China how to bring about substantive progress (in denuclearizing the North).”

By Shin Hyon-hee (heeshin@heraldcorp.com)