A former top American diplomat in Taiwan has warned that the island’s security relationship with the United States is being jeopardized by escalating Chinese espionage.

William Stanton, who retired last year as head of the American Institute in Taiwan, the de facto U.S. Embassy, said the “success and frequency” of spying cases have served to “undermine U.S. confidence in security cooperation with Taiwan.”

In recent years, at least nine Taiwanese have been arrested for spying for mainland China. They include an army general and an air force captain accused of passing information about Taiwan’s air-defense systems to China.

Stanton said he was speaking in a personal capacity. But his comments Friday marked an unusual break from U.S. support for Taiwan’s growing economic relationship with China, which U.S. officials encourage to reduce the chance of war.

Although the United States does not officially recognize the Taipei government, it is the island’s only major arms supplier. The United States is also required by law to maintain the ability to defend Taiwan. The American Institute in Taiwan is officially a private organization, but it is funded largely by the U.S. State Department.

China claims Taiwan as part of its territory and has threatened to use force to take the self-governing island if it were to declare de jure independence. While that military threat means few on the island seek full independence, the vast majority of Taiwanese also oppose formal unification with the mainland.

But relations between Beijing and Taipei have warmed under President Ma Ying-jeou. Ma has signed a series of trade pacts with China and opened direct flights with China to boost Taiwan’s economy and calm what had been a tense cross-strait relationship under the island’s previous pro-independence administration.

Stanton also criticized Taiwan’s growing economic ties with Beijing, saying they hamper increased trade and political ties with the rest of the world.

“The risk of dependency on trade gives China leverage against Taiwan that is dangerous so long as the two sides remain politically divided,” he said. “I worry because I sometimes think the Taiwanese people do not worry enough.”

Stanton said the growing number of Taiwanese spying for China may be attributable to lower morale in the armed forces because of Taiwan’s low defense spending. While China continues to increase military spending, Taiwan last year spent only 2.2 percent of its gross domestic product on defense, down from 3.8 percent in 2004.

The former U.S. official was speaking to a group of pro-independence Taiwanese, many of them elderly emigres to the United States who had returned for the event. Su Tseng-chang, the leader of Taiwan’s opposition Democratic Progressive Party, which also criticizes Ma for improving ties with Beijing, was in the audience as well.

Taiwan’s government hit back at Stanton’s remarks, with the Defense Ministry saying its work on counterespionage had been effective.

— Financial Times