* New Chinese rules took effect at start of year
* Follow creation of controversial air defense zone
* U.S. challenged air zone with B-52 flight (New throughout, adds details and background; adds byline)
By David Brunnstrom
WASHINGTON, Jan 9 The United States, already at odds with China over that country's air defense zone, said on Thursday that new Chinese fishing restrictions in disputed waters in the South China Sea were "provocative and potentially dangerous."
The legislature of China's Hainan province approved rules in November that took effect on Jan. 1 requiring foreign fishing vessels to obtain approval to enter waters under its jurisdiction.
Such a move, if broadly enforced, could worsen tensions in the region. Beijing claims almost the entire oil- and gas-rich South China Sea, rejecting rival claims to parts of it from the Philippines, Taiwan, Malaysia, Brunei and Vietnam.
"The passing of these restrictions on other countries' fishing activities in disputed portions of the South China Sea is a provocative and potentially dangerous act," State Department spokeswoman Jen Psaki told a news briefing.
"China has not offered any explanation or basis under international law for these extensive maritime claims."
"Our long-standing position has been that all concerned parties should avoid any unilateral action that raises tensions and undermines the prospects for a diplomatic or other peaceful resolution of differences."
The fishing rules followed China's creation of an air defense identification zone in late November above the East China Sea in an area that includes islands at the heart of a bitter territorial dispute with Japan.
The United States responded to the declaration of the air zone by sending two B-52 bombers into the area without informing China. At the same time, it advised U.S. carriers to operate in line with so-called notices to aviators issued by foreign countries.
The State Department spokeswoman gave no indication of any possible U.S. response to the fishing zone.
HAINAN HOME TO CHINESE CARRIER
According to the website of the Hainan legislature, foreign fishing vessels need approval to enter from the "relevant and responsible department" of the Chinese government's Cabinet.
Hainan is home to Chinese naval facilities that include a purpose-built dock for the country's only aircraft carrier as well as a base for attack submarines.
Hainan, which juts into the South China Sea from the country's southern tip, says it governs 2 million square km (770,000 square miles) of water, according to local government data issued in 2011. The South China Sea is an estimated 3.5 million square km (1.4 million square miles) in size.
The Hainan rules do not outline penalties, but the requirements are similar to a 2004 national law that says boats entering Chinese territory without permission can have their catch and fishing equipment seized and face fines of up to 500,000 yuan ($82,600).
Philippine Foreign Affairs Department spokesman Raul Hernandez said Manila had asked its embassy in Beijing to get more information on the rules.
Hainan officials were not immediately available to comment, but Foreign Ministry spokeswoman Hua Chunying said regulating the use of China's marine resources was a normal practice.
"The goal is to strengthen the security of fisheries resources and to openly and reasonably utilize and protect fisheries resources," Hua said at a regular news briefing when asked about the rules.
Chinese enforcement of the fishing zone could depend on the nationality of the fishermen, said Shi Yinhong, an international relations professor at Renmin University in Beijing.
"I think Hainan put it out to tell relevant countries we have such a regulation, but how we practice it depends on how bilateral relations are," Shi said.
"If ties are good, the regulation may be loose. If not, we will practice it strictly, which means that you have to get approval from us before entering."
China's ties with the Philippines have been especially frosty over the South China Sea. (Reporting by David Brunnstrom; addtional reporting by Manuel Mogato in Manila and Sui-Lee Wee, Huang Yan and Megha Rajagopalan in Beijing; Editing by Peter Cooney and David Gregorio)