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The area is at the center of heightened tensions between the U.S. and China

It was not immediately clear the reason why the USS Stennis was denied entry

CNN  — 

China has denied a U.S. aircraft carrier entry into a Hong Kong port, according to Pentagon spokesman Cmdr. Bill Urban.

“We were recently informed that a request for a port visit by a U.S. carrier strike group, including the USS John C. Stennis and accompanying vessels, to Hong Kong was denied,” he said. “We have a long track record of successful port visits to Hong Kong, including with the current visit of the (command ship) USS Blue Ridge, and we expect that will continue.”

It was not immediately clear why the Stennis was denied port access.

A spokesman for the Hong Kong Security Bureau declined to comment on the decision, saying the Hong Kong Special Administrative Region government wouldn’t comment on the individual visit application of foreign warships.

The port access denial comes just two weeks after Defense Secretary Ash Carter visited the Stennis while the carrier was operating in the South China Sea. The area is at the center of heightened tensions between the United States and China, with Beijing building and militarizing man-made islands in the contested waters.

“We want to reduce tensions, but we also want everybody in the region to be able to rise and develop in their own way – including the Philippines, by the way, which happens also to be a longstanding and very staunch treaty ally of the United States,” Carter said while addressing crew and reporters on board.

China has turned down access requests from the U.S. military in the past. In 2007 the frigate USS Reuben James, planning a holiday port call for crew at the end of December, was refused entry. That same year China also refused to allow the aircraft carrier USS Kitty Hawk battle group into Hong Kong for a Thanksgiving holiday port call.

At the time of the 2007 port denials, China was critical of U.S. arms sales to Taiwan.

The Stennis, a 97,00-ton, 1,100-foot-long Nimitz-class carrier, and ships in its strike group first entered the South China Sea this year on March 1, with the Chinese navy apparently keeping close watch.

“We have Chinese ships around us that we normally didn’t see in my past experience,” Capt. Greg Huffman, Stennis’ commanding officer, said in the Navy release in early March.

The Navy said at that time that the presence of the Stennis group was a routine deployment.

But the release from the U.S. Seventh Fleet release mentioned other “similar” movements that have had a broader mission.

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One example includes the guided missile destroyer USS Curtis Wilbur in January, which was described by the U.S. Defense Department as intended to challenge “excessive maritime claims that restrict the rights and freedoms of the United States and others.”

“This operation demonstrates, as President (Barack) Obama and Secretary (Ash) Carter have stated, the United States will fly, sail and operate anywhere international law allows. That is true in the South China Sea, as in other places around the globe,” the Pentagon said at the time.

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And earlier this month, U.S. Pacific Command began flying A-10 Thunderbolt jets and HH-60 Pave Hawk helicopters out of Clark Air Base in the Philippines with part of their mission “assuring all nations have access to air and sea domains throughout the region in accordance with international law,” according to an Air Force press release.

The Air Force said the aircraft would be flying in international airspace near Scarborough Shoal, which is claimed by both China and the Philippines and lies around 130 miles from the Philippines’ capital of Manila.

CNN’s Barbara Starr contributed to this report.