Visiting Taiwan government spokesman Philip Yang said the island’s engagement with mainland China in the past three years, resulting in a landmark economic cooperation pact in 2010, has eased tensions across the Taiwan Strait and in east Asia.

He told a Washington news conference, however, that US support for Taiwan’s self-defense remains vital.

“Cross-straits policy is of utmost importance to security in east Asia and Washington’s continued support of Taiwan accords with American security and economic interests in the region,” Yang said.

While Taiwan President Ma Ying-jeou’s pro-engagement policy has calmed six decades of animosity, he still seeks F-16 C/D fighter jets, which he says are needed to maintain a deterrent and give Taipei leverage in future negotiations with China. His government also is seeking upgrades of its existing fleet of less-advanced F-16 A/B jets.

Washington has yet to announce whether it plans to supply the C/Ds, a move that would especially anger mainland China, which opposes all arms sales to Taiwan and regards the democratically governed island as part of its territory. The last US announcement of weapons sales in 2010 prompted China to sever military ties with the US for nearly a year.

Speculation is growing that the Obama administration, which has sought to improve relations with Beijing, would agree only to the upgrades.

Yang, a former adviser to Taiwan’s National Security Council, dismissed as guesswork reports that Vice President Joe Biden would inform Beijing during a visit next month that the US would not supply the F-16 C/Ds that Taiwan seeks.

The United States is legally obligated to supply Taiwan with defensive weapons, and to do so without consulting China beforehand. Yang said he was confident that the US would observe that commitment.

Asked about Taiwan’s defense capabilities, Yang said Taiwan would be able to maintain a “sufficient degree of deterrence” in the future. But he noted advances in China’s air force and its test early this year of its own low-visibility stealth fighter. He said Taiwan’s fleet of F-5 fighters were “very old if not antique” and that its current batch of F-16s were more than 15 years old.

Taiwan split from China amid civil war in 1949. Beijing has threatened to invade if Taiwan ever declares independence, which Ma has no intention of doing.