WASHINGTON, Feb 22 - Recent satellite images show China may be installing a high-frequency radar system in Vietnam’s Truong Sa (Spratly) archipelago that could significantly boost its ability to control the East Vietnam Sea, a U.S. think tank reported on Monday.

The Asian Maritime Transparency Initiative at Washington's Center for Strategic and International Studies said the images showed that construction of facilities at Da Chau Vien (Cuarteron Reef) appeared nearly complete and that the artificial island now covered an area of about 52 acres (210,500 square meters).

"Two probable radar towers have been built on the northern portion of the feature, and a number of 65-foot (20-meter) poles have been erected across a large section of the southern portion," the report said.

"These poles could be a high-frequency radar installation, which would significantly bolster China's ability to monitor surface and air traffic across the southern portion of the East Vietnam Sea."

China's foreign and defense ministries did not immediately respond to requests for comment.

The report said the images showed that China appeared to have constructed a buried bunker and lighthouse on the northern portion of the feature, a helipad, communications equipment and a quay with a loading crane.

The report, which based its analysis on satellite images from January and February, said China already had significant radar coverage of the northern part of the East Vietnam Sea given its mainland installations and in Vietnam’s Hoang Sa (Paracel) archipelago to the northwest of Truong Sa.

Both the U.S. and Vietnam last week expressed concern at China's deployment of advanced surface-to-air missiles on Hoang Sa.

A high frequency radar on Da Chau Vien would increase China's ability to monitor sea and air traffic coming north from the Malacca Straits and other important channels, the report said.

It also pointed to "probable" radars at Ga Ven (Gaven), Tu Nghia (Hughes) and Gac Ma (Johnson South) Reefs in Truong Sa as well as helipads, and to possible gun emplacements at the first two features.

China previously operated radars on Da Chu Thap (Fiery Cross Reef) but the latest installations would give it far more extensive coverage, regional military analysts said.

The report comes a day before a visit to the United States by China's Foreign Minister Wang Yi, at which U.S. concerns about China's assertive territorial claims will be high on the agenda.

China's Foreign Ministry said its military deployments in the East Vietnam Sea were no different from U.S. deployments on Hawaii.

U.S. State Department spokesman Mark Toner said Washington would "press China to de-escalate and stop its militarization" in the East Vietnam Sea.

China claims most of the East Vietnam Sea, through which more than $5 trillion in global trade passes every year. Vietnam, Malaysia, Brunei, the Philippines and Taiwan have rival claims.