Taiwan's President Ma Ying-jeou startled friends and rivals by making his closest advisor "ambassador" to the United States on a mission to prove that the island is still a key ally.

King Pu-Tsung, was considered the power behind the Taiwanese throne as the president's election strategist and former head of the ruling Kuomintang party. But he has never been a diplomat, and the appointment surprised the United States and China -- the rival powers who underpin Taiwan's security and economy.

In an interview with AFP, King highlighted the importance of the "strategic ambiguity" that the island of 23 million people maintains with its neighbor, on one side, and protector, on the other.

That ambiguity does not help counter US observers who say Taiwan has become a "strategic liability" because of the harm that US arms sales to Taiwan -- about $180 billion since 2008 -- do to relations with China.

"We have our own pragmatic approach to survive," said the envoy who cannot call himself ambassador, as the United States broke formal ties with Taiwan in 1979 when it recognized China.

"We need strong support from the United States, but we also have to deal cautiously with mainland China because now they they are the number one partner of Taiwan," he added.

"It is a very strategic ambiguity that we have. It is the best shield we have."

King said Taiwan-US relations were "damaged" under previous president Chen Shui-bian, and his job is to lead "low profile," "pragmatic" attempts to lift Washington's confidence.

His links to President Ma are important. "What I say can probably represent what he is thinking in the future," he said.

President Ma wants advanced US weaponry. Despite the improved atmosphere, China has not renounced its threat to use force if Taiwan moves too far away from the ambiguous truce that has lasted since the communist-nationalist split in 1949.

"We still need to have a very strong defense capability to protect Taiwan," said the envoy, who has his eyes on American F-22 or F35 fighter jets and submarines. Such a sale would infuriate Beijing.

"Even if it is just a symbolic gesture, it is very important to us. It shows strong US support to Taiwan," said King.

Talks on a Trade and Investment Agreement, which could lead to a full free trade deal, are to resume in March. Taiwan lifted a six-year-old ban on imports of some US beef to tempt the US administration back into talks.

Weapons and trade are all part of what King calls the "paradoxical" relations between the United States and the island.

US-Taiwan relations are "the best they have been in the past 30 years," King, who took up his post in December, insisted.

However the United States encourages Taiwan to have good relations with China. "But like a lot of people in the think tanks, they are worrying that probably Taiwan is leaning toward mainland China too much."

King said the message he gets is: "'You have cordial relations, beneficial relations with mainland China, but don't go too far'."

According to Richard Bush, a former head of the US mission in Taiwan and now director of the Brookings Institution's Center for Northeast Asian Policy Studies, some US "observers believe that Taiwan has become a strategic liability" so the United States should stop arming Taiwan.

The doubters include Zbigniew Brzezinski, national security adviser under President Jimmy Carter, and Bill Owens, a retired admiral who was a vice chairman of the US chiefs of staff.

"They echo Chinese diplomats who argue that our arms sales are the major obstacle to good US-China relations," Bush said in a policy paper for Brookings released last month.

Bush added however that new Taiwan-China improvements will probably only be "modest" and could stall.

George Tsai, political science professor at Chinese Culture University in Taipei, said King's close links to the president made him the perfect candidate to help disperse US concerns.

"Washington has sent messages to Taipei that it wants to the keep the status quo across the Taiwan Strait," said Tsai.

"Washington has revealed its concerns on some issues like the proposed culture agreements and confidence building measures, which it believes does not serve US interests," Tsai said.

King said a US rethink was "wishful thinking" and there was nothing ambiguous in President Ma's comment that he would "rather die" than give up Taiwan's sovereignty.