Taiwan has effectively dropped a request for US submarines to help shore up the balance of power with political rival China, a military source said on Tuesday, dissolving what could be a new rift in tense Sino-US ties.                                            Defence officials on the island that has fallen behind in the military balance of power with China had agreed with Washington in 2008 to a study on upgrading Taiwan's ageing submarine fleet but will stop pushing the item to keep peace with Beijing, said a source close to the defence ministry in Taipei.                                            "Taiwan isn't asking for the submarines anymore," the source told Reuters. "The biggest consideration was the warming of relations with mainland China."                                            China has blasted the United States over a planned $6.4-billion arms package for Taiwan, saying it would place sanctions on US firms that sell weapons to the island.                                            
The package would include Patriot missiles and Black Hawk transport helicopters, also part of the 2008 agreement.                                            Taiwan still hopes to get advanced US-made F-16 jets though, to boost its existing fleet to deal with China's growing numbers of Russian-designed Su-30 and Su-27 fighters.                                            A submarine sale would further ignite Beijing's anger toward Washington and could turn it against Taiwan, which has avoided China's wrath over the recent arms proposal.                                            Taiwan has sought peace with China since Beijing-friendly island president Ma Ying-jeou took office in 2008, brokering a series of trade and tourism deals.                                            China has claimed sovereignty over self-ruled Taiwan since 1949, when Mao Zedong's forces won the Chinese civil war and Chiang Kai-shek's Nationalists fled to the island. Beijing has threatened to attack if Taiwan declares formal independence.                                            Taiwan's navy includes four submarines, two of which date from World War Two and are now used only for training, according to GlobalSecurity.org.                                            China has more than 60 submarines, some capable of carrying nuclear ballistic missiles.                                            "My guess is that the submarine issue is sunk, never to surface again," said Ralph Cossa, president of the US think tank Pacific Forum CSIS.