The Reagan administration, seeking to avert a falling out with the People's Republic of China, has decided against selling new high performance jet fighters to Taiwan, informed sources said yesterday.

The administration decision reached late last week in long-awaited White House discussions, is being conveyed to Peking by John H. Holdridge, assistant secretary of state for East Asian and Pacific affairs, who flew to the Chinese capital over the weekend.

The State Department, confirming Holdridge's journey, would only say last night that he and a team of specialists will discuss with Chinese officials "international and bilateral matters of mutual concern," including the hotly contested issue of continuing U.S. arms sales to Taiwan.

Informed sources said Holdridge would tell the Chinese leaders that the administration will not provide Taiwan with either the FX fighter plane or the Harpoon anti-ship missile, weapons more sophisticated than those sold to the Nationalist Chinese island by previous administrations.

At the same time Holdridge is expected to make clear that sales of other weapons will continue, including new sales of the F5E fighter plane which is already a mainstay of Taiwan's arsenal.

According to congressional sources, the administration has decided to divide its continuing sales to Taiwan into six parts to be submitted to Congress at two-month intervals throughout the year.

In recent months China has postponed talks on enhanced military cooperation, including Sino-American arms deals, due to concern about the potential sale of high profile aircraft to Taiwan. China also threatened to downgrade diplomatic ties with Washington if the sale were consummated.

The Chinese authorities also took a much stronger public stand than before against continuation of the existing level of U.S. arms supply to Taiwan. Because the Chinese leaders' tolerance level seemed to be shifting--they reportedly have been demanding a firm time limit on future Taiwan arms transactions--it was uncertain how they would react to Holdridge's message.

There is no doubt that Taiwan and its backers in the United States would be sorely disappointed by the administration's decision.

Ronald Reagan long had been counted as a special friend of Taiwan based on close ties before his election to the presidency, and Taiwan had high hopes that he would act in its favor in the White House.

President Reagan is reported to have assured Sen. Jesse Helms (R-N.C.) in a recent conversation that the Taiwanese would be permitted to buy "all that they need" in U.S. arms. Part of the rationale for withholding the FX fighter, however, is a U.S. military assessment that the sophisticated aircraft are not required for Taiwan's defense at this time.

A recent U.S. intelligence assessment concluded that the pace of China's military modernization has slowed, thus diminishing the potential threat to the island. Moreover, China's public offers of political accommodation with Taiwan have reduced the level of tension in the Taiwan Straits.

Secretary of State Alexander M. Haig Jr. is known to have been particularly cautious about a Taiwan sales program that could jeopardize the U.S. "strategic relationship" with Peking. This relationship took on additional urgency, in the eyes of some officials, in view of the heightened East-West tensions arising from the martial law crackdown in Poland.

For many months Taiwan has been acquiring Northrop F5E fighter under co-production arrangements that permit much of the manufacture on the island.

Saying that a more powerful aircraft was needed, the Taiwanese requested an "FX"--either General Dynamics' F16/79, a low-powered model of the high performance F16, or Northrop's F5G Tiger Shark, the next generation model of the F5 series.

Among the possible solutions to the Taiwan arms struggle under discussion was technological upgrading of the F5E to allow Taiwan greater military capability without providing the political symbolism of a more advanced aircraft model. It was unclear last night whether the administration's plans will permit such an improvement in Taiwan's aircraft.