YOKOSUKA NAVAL BASE, Japan -- A Chinese surveillance ship has been detected observing the Valiant Shield military exercise from within the United States' exclusive economic zone -- a move the U.S. actually doesn't mind.
One Chinese auxiliary general intelligence vessel has been watching most of Valiant Shield since it began Sept. 15 in and around Guam, military officials said Monday.
Valiant Shield comes in the midst of tensions in the Asia-Pacific region, much of which involve China's rapidly modernizing military and its territorial ambitions.
China stakes an ambiguous claim to about 90 percent of the South China Sea, including areas that the most nations consider international waters.
In recent years, Chinese ships have harassed U.S. ships operating in the international waters that compose China's exclusive economic zone, or EEZ -- mostly notably in 2009, when the USNS Impeccable was surrounded by five vessels.
Chinese ships have repeatedly been observed within United States EEZ borders in the past year. U.S. officials have stated they hope the moves will persuade China to shift its position against foreign military movements in its EEZ.
"We'd like to reinforce that military operations in international commons and outside of territorial waters and airspace is a fundamental right that all nations have," Valiant Shield spokeswoman Lt. Cmdr. Kim Dixon said Monday. "The Chinese were following international norms, which is completely acceptable."
An EEZ extends as far as 200 nautical miles from a nation's borders. EEZs confer fishing, mining and other economic rights, but they are not territorial waters belonging to any one country.
EEZs make up about one-third of the world's oceans. The United States and most other nations interpret international law to allow militaries to conduct surveillance in EEZs, but China and about 20 other nations generally see things differently.
On Aug. 19, a Chinese fighter jet intercepted a U.S. Navy P-8 flying 135 miles from Hainan Island, within China's EEZ.
The armed jet performed a barrel roll and flew within 20 feet of the P-8's wingtip, Pentagon spokesman Rear Adm. John Kirby said Aug. 22.
Kirby condemned the "unsafe and unprofessional intercept, which posed a risk to the safety and the well-being of the aircrew, and was inconsistent with customary international law."
The Pentagon later released photos of the Chinese fighter displaying its armed underside to the P-8, a surveillance plane with a body resembling a commercial airliner.
Chinese officials said their pilot acted professionally and called on the U.S. to end "close-in" surveillance.
China also sent a surveillance ship to the EEZ surrounding Hawaii during the multinational Rim of the Pacific exercise this past summer. That decision, while in accordance with U.S. views on EEZs, surprised some military officials because China was also an exercise participant.
China's surveillance of Valiant Shield was far less surprising. Much of the exercise has focused on countering "anti-access, area denial" -- a strategy that stops militaries from entering international waters and airspace, and prevents any forces already within those spaces from maneuvering.
The Pentagon's annual report to Congress on China's military stated that Beijing is producing advanced long-range missiles and other weaponry to prevent access to large parts of the South and East China seas. The other country most often associated with an anti-access, area denial strategy is Iran.
Iranian media reported that the ships arrived in Bandar Abbas for joint exercises. China's Xinhua news agency reported that the 17th Chinese escort naval fleet would be in Iran for five days.