Tensions in the South China Sea are rising, pitting China against smaller and weaker neighbors that all lay claim to islands, coral reefs and lagoons in waters rich in fish and potential gas and oil reserves. China's recent construction of artificial islands in the Spratly archipelago, complete with airstrips and radar stations, and U.S. patrols challenging Beijing's vast territorial claims, have caused concern that the strategically important waters could become a flashpoint.
A look at some recent key developments:
EDITOR'S NOTE: This is a weekly look at the latest key developments in the South China Sea, home to several territorial conflicts that have raised tensions in the region.
SCARBOROUGH SHOAL AS A RED LINE
Being so close to the main Philippine island of Luzon, the Scarborough Shoal is a particularly sensitive piece of real estate.
The uninhabited coral reef was exploited by both Filipino and Chinese fishermen, and was used by as a bombing range by the U.S. Air Force until Washington closed bases in the Philippines in 1991. In 2012, Chinese vessels seized the shoal following a tense standoff with Filipino ships.
The South China Morning Post reported this week, citing an anonymous military source, that Beijing will start reclamation work on the shoal later this year and may add an airstrip to extend the air force's reach. Transforming the shoal into another military outpost so close to Manila and the busy Luzon Strait, which connects the South China Sea with the Pacific Ocean, would be the biggest challenge yet for the Philippines and its ally, the U.S.
China did not confirm or deny the report.
The Philippines has contested China's vast claims in the South China Sea at a U.N. tribunal, which is expected to rule soon in what many believe will be an unfavorable outcome for Beijing. China has refused to take part in the proceedings, and there are worries whether it might respond by cementing its island holdings, or even expanding them by fortifying Scarborough, too.
Jay Batongbacal, director of the University of the Philippines College of Law's Institute for Maritime Affairs and Law of the Sea, cited historical documents showing the United States ceded the shoal to the Philippines as part of American administered territory at independence in 1946. This is evidence that the shoal is covered by the Mutual Defense Treaty, and thus the U.S. has an obligation to prevent it from being permanently controlled by China, he said.
The shoal, therefore, represents "a red line" to the U.S. and its allies, he said.
China says Huangyan Island — Chinese for Scarborough — appears on maps as Chinese territory starting in 1935.
Last week, the new U.S. Air Force contingent from Luzon flew sorties near Scarborough, drawing a mild rebuke from China.
The Wall Street Journal quoted U.S. officials as saying that Navy ships canceled a freedom of navigation operation scheduled for April in order to "lower the temperature" in the South China Sea.
U.S. LAWMAKERS WANT MORE NAVAL OPERATIONS
Members of Congress are urging the Obama administration to order more naval operations in the South China Sea.
"I don't know why we are not doing it weekly, or monthly," said Republican Sen. Bob Corker, chairman of the Senate Foreign Relations Committee, noting the U.S. has about 60 percent of its naval vessels in the Pacific region.
Sen. Cory Gardner said sending U.S. ships into the area every three months "is simply insufficient to send a strong message to China."
Deputy Secretary of State Antony Blinken said that such operations will take place regularly.
Blinken agreed with Sen. Marco Rubio that China's objective was control of the entire South China Sea. Blinken said China was alienating its neighbors and risked "conflict, instability and isolation" unless it changed its approach and clarified its claims in accordance with international law.
CHINA'S 'CONSENSUS' WITH 3 ASEAN MEMBERS QUESTIONED
Chinese Foreign Minister Wang Yi's statement that Beijing had reached a consensus with Brunei, Cambodia and Laos on the South China Sea has been met with some skepticism — and concern from other ASEAN members.
Cambodian government spokesman Phay Siphan said that no new agreement with China on the issue has been reached.
Laos and Vietnam, which is also squabbling with China, issued a joint statement pledging to accelerate the settlement of disputes in line with international law. They also called for a binding Code of Conduct to govern disputes, something Beijing has been reluctant to conclude.
Singapore's senior diplomat, Ong Keng Yong, said Beijing may be trying to split the regional bloc.
"Having (the Chinese) foreign minister announce that two of non-claimant states, namely Cambodia and Laos, have decided that they are not going to do this and that, seems to me like interfering in the domestic affairs of ASEAN," said the former ASEAN secretary general. China asked Singapore to clarify Ong's comments.
"No matter how many and how frequently U.S. ships come to the South China Sea, that would not change the fact that the islands and adjacent islands are China's inherent territory, it would not stop the pace of China's growth and development and even more it would not shake the will of the People's Liberation Army in resolutely safeguarding the sovereignty and security of China." — Chinese Defense Ministry spokesman Col. Wu Qian.
Associated Press writers Hrvoje Hranjski in Bangkok, Christopher Bodeen in Beijing, Jim Gomez in Manila, Philippines, and Matthew Pennington in Washington contributed to this report.
Follow Hranjski on Twitter at twitter.com/hatbangkok
Gomez at www.twitter.com/JimSGomez