WASHINGTON--Two aircraft carrier strike groups of the U.S. Navy's 7th Fleet have been deployed since mid-September to the Western Pacific in an apparent attempt to keep the activities of the Chinese military in check amid growing Japan-China tension over the Senkaku Islands.

The two nuclear-powered aircraft carriers are the USS George Washington, based in Yokosuka, Kanagawa Prefecture, and the USS John C. Stennis, based on the U.S. west coast. The command of the 7th Fleet is also located in Yokosuka.

It is unusual for the U.S. Navy to simultaneously deploy two strike groups each comprising an aircraft carrier and escort ships to the West Pacific. Analysts believe the move is aimed to hold the Chinese military in check in light of the recent tension between Tokyo and Beijing over the islands in Okinawa Prefecture in the East China Sea. The deployment is also believed to be a response to China's launch of its first aircraft carrier in September.

According to Strategic Forecasting Inc., a U.S. private information firm known as Stratfor, and others, the George Washington Strike Group sailed northwest after training off Guam, arriving in waters east of Taiwan on Wednesday. The Stennis was deployed near the Senkaku Islands on Sept. 26 before passing through the South China Sea, and is currently operating in waters near Malaysia, according to Stratfor and others.

Japanese government sources agree that the deployment of the two strike groups was prompted by the tension between Japan and China.

The U.S. government has stated that the Senkaku Islands "clearly" fall under Article 5 of the Japan-U.S. Security Treaty, which requires Washington to defend Japan in the event of an armed attack.

Deploying two aircraft carriers is "a demonstration of the United States' resolve to act in line with Article 5" and to support the Japan-U.S. alliance, a senior official of Japan's Defense Ministry said.

The deployment was preceded by requests from Japan through unofficial diplomatic channels for concrete U.S. action in connection with the upsurge in Japan-China tension, the official said.

The United States has publicly called for both China and Japan to maintain cool heads when dealing with the issue.

According to a high-ranking Foreign Ministry official, many in the government believe the U.S. aircraft carrier deployment is a sign that Washington believes Tokyo should deal effectively with the dispute to reach a prompt resolution.

One of the few times the United States has deployed two aircraft carriers to the West Pacific was during the Taiwan Straits crisis in the spring of 1996, when tension between China and Taiwan skyrocketed.