The United States announced last week that they would not sell new F-16 aircraft to Taiwan but upgrade the island nation’s existing fleet of fighter jets instead.

The move is widely interpreted as an attempt to appease China which regards Taiwan as a renegade province and vehemently criticized an American arms sale to the country last year.

The Obama Administration argues that upgrading Taiwan’s current fleet of F-16s will make the aircraft nearly as capable as the 66 newer models which Taipei had requested. The upgrades reportedly do not include improved engines however which will make it more difficult for the Taiwanese to retire their older jets.

The administration was under pressure from opposition Republicans who are critical of its willingness to water down a weapons deal because of Chinese objections. Conservative lawmakers worry that America may be losing its previously uncontested superiority in the Pacific as China is rapidly expanding and modernizing its armed forces.

Taiwan needed to boost its air defenses as some 70 percent of its fighter fleet was supposed to retire over the next decade.

China has invested heavily in enhancing its air and missile strike capabilities in recent years, causing a security imbalance to develop across the Taiwanese Strait that America is unlikely to be able to mend with military force alone.

In the near future, the United States will probably not be able to bring enough fighter jets to battle to offset China’s quantitative superiority. It hasn’t enough planes stationed nearby, on Taiwan nor in Japan, and could not dispatch enough aircraft carriers to the site in time to effectively repel an invasion.

The Taiwanese air force meanwhile is increasingly vulnerable to a Chinese missile attack which could destroy all of Taiwan’s airfields in a single strike, rendering its fixed-wing airpower virtually useless.

In short, the United States and Taiwan can no longer be confident of winning the battle for the air in the air.

In order to restore balance, the United States could disperse fighter planes across a larger number of bases or seek to pose the same kind of threat to China’s air force bases as it presents to those on Taiwan and Okinawa, Japan. That would require fielding hundreds of additional midrange missiles on Taiwan which neither America nor Taiwan currently operates.

The alternative would be to make abundantly clear that an attack against Taiwan would be considered an attack on the United States but Washington may not be willing to go to war with China over the issue, especially as the two great powers’ economic interests are so intertwined.

China, moreover, is far less likely to stage an invasion of Taiwan today than it may have been fifteen years ago. As Robert D. Kaplan points out in The Washington Post, it doesn’t need to anymore.

The trend line suggests that China will annex Taiwan by, in effect, going around it: by adjusting the correlation of forces in its favor so that China will never have to fight for what it will soon possess.

Not only does China have some 1,500 short range ballistic missiles focused on Taiwan, Kaplan notes, but there are more than a thousand commercial flights between the island and mainland China every month and close to a third of Taiwanese exports go to China. “Such is independence melting away.”

And as China’s strategic planners need to concentrate less on capturing Taiwan, they will be free to focus on projecting power into the energy rich South China Sea and, later, into the adjoining Indian Ocean.

It is in the South China Sea where the United States declared stability to be of “national interest” last year. “People want to see the United States fully engaged in Asia,” said Secretary of State Hillary Clinton in January 2010, “so that as China rises the United States is there as a force for peace.”

America isn’t giving up on Taiwan, especially as outright Chinese control of the island would enable Beijing to enforce its claims to sovereignty over the South China Sea and bar foreign military forces from crossing the Luzon Strait. But it is adjusting to a new reality in East Asia. China is a regional power to be reckoned with. If Washington is to frustrate its ascendancy, it has to pick its battles carefully.