Tokyo and Washington will deploy advanced Patriot interceptor missiles in Japan for the first time, officials said Monday amid concerns North Korea may be preparing to test-fire a long-range ballistic missile.

The U.S. and Japan reached an accord on the interceptors this month after reports of the possible test-firing became public, and they plan to install the weapons on American bases in Japan as soon as possible, Japan's Defense Agency said.

Japan's largest newspaper said the interceptor missiles could be installed by the end of the year.

It was unclear whether Patriot Advanced Capability-3 missiles — designed to intercept ballistic missiles, cruise missiles or enemy aircraft — would be able to hit North Korea's latest long-range missile, the newspaper reported.

Yomiuri Shimbun said the medium- to long-range interceptor may be unable to shoot down the Taepodong-2, which is believed capable of reaching parts of the United States. The newspaper did not cite a source for that assessment.

CountryWatch: North Korea

The Defense Agency spokeswoman said the sites of the Patriot deployment and its timing have not been decided.

Yomiuri Shimbun said that the U.S. military would deploy three or four of the surface-to-air missile batteries on the southern island of Okinawa by the end of the year, and send an additional 500 to 600 U.S. troops there. Up to 16 missiles can fit in a single PAC-3 battery, according to the system's manufacturer, Lockheed Martin Corp.

The plan was proposed by U.S. officials during a June 17 meeting in Hawaii, the newspaper reported, quoting unidentified government officials.

Intelligence reports have said North Korea may be fueling the Taepodong-2, one of its most advanced missiles, at a launch site on the country's northeastern coast. Japan's defense chief said that it was not clear if fueling was taking place, a news report said.

Defense Agency head Fukushiro Nukaga said in a speech in Osaka that while "it appears to be a fact that the missile has been mounted on a launch platform," it was unclear if it was being fueled, Kyodo News agency reported.

The North has maintained a self-imposed moratorium on such launches since 1999. The United States, Japan and other countries have urged North Korea to halt any plans to test the missile. Pyongyang has insisted it has the right to test-launch.

South Korean Foreign Minister Ban Ki-moon was traveling to Beijing on a two-day visit to seek China's cooperation in halting a launch.

"There is a growing need to intensify discussions between South Korea and China on North Korea's recent missile issue and the nuclear issue," the South Korean Foreign Ministry said in a statement.

China is the North's key ally and is believed able to exert the most influence on Pyongyang. Beijing has hosted international talks on the North's nuclear program, which halted in November amid North Korean boycott anger over U.S. financial sanctions.

The missile concerns also have prompted the U.S. to move up a test of a missile-detecting radar system in northern Japan, Kyodo News agency reported, citing an unidentified U.S. official in Washington.

Kyodo said testing of the high-resolution radar capable of detecting incoming missiles could start as early as Monday, weeks earlier than expected.

Japanese officials said the report could not immediately be confirmed.

The X-Band radar has been transferred from a U.S. base in Japan to the Japanese Air Self-Defense Force's Shariki base at Tsugaru, 360 miles northeast of Tokyo.

The radar deployment is part of the joint missile defense project, which began after North Korea fired a missile, part of which flew over Japan, in 1998.

Tokyo and Washington on Friday also signed an agreement to expand their cooperation on a joint ballistic missile defense shield, committing themselves to joint production of interceptor missiles.