China's official New China News Agency today condemned an agreement signed Thursday in Washington, charging that it grants diplomatic status to Taiwanese representatives in the United States in "open violation" of U.S. understandings with Peking.

The accord was signed by the two nongovernmental bodies set up by Taiwan and the United States to maintain trade and cultural ties following the break in formal diplomatic relations almost two years ago. That break came at the insistence of the People's Republic of China, which claims Taiwan.

[A State Department official, acknowledging that the new accord provides "nondiplomatic immunity" to persons assigned to the bodies in Taipei and Washington, said the act establishing the nongovernmental entities specifically provides for such an arrangement. She said talks working out the details had been underway for some time.]

The Chinese news agency recalled that "after the normalization of Sino-U.S. diplomatic relations, the American government has repeatedly stated that the relations between the United States and Taiwan are 'unofficial, nongovernmental.'

"Now the U.S. government publicly swallowed its own words. This is indeed surprising."

The dispatch was datelined Washington but the strong, unattributed language indicated this was China's official reaction.

The Chinese news agency had not used such strong language toward the United States since Ronald Reagan broached the subject of official relations with Taiwan this summer. At that time the official Chinese press declared that upgrading relations between Washington and Taipei would "destroy" the basis of Sino-U.S. relations.

Tonight's dispatch stopped just short of that. "There is no doubt that the American Institute in Taiwan and the Taiwan Coordination Council for North American Affairs agreement, sponsored by the U.S. government and the Taiwan authorities, will hurt the feelings of the Chinese people and give rise to widespread concern and indignation in China," the dispatch said.

It quoted an "American observer" in Washington as commenting that "in theory the United States and Taiwan have only nongovernmental links, but in practice, virtually all the trappings of a fullblown diplomatic relationship are now in existence."

The news agency said, "This is an open violation of the agreement between the United States and China and the joint communique on the establishment of diplomatic relations between the two countries."

The agency said it granted officials of the two organizations immunity from taxation or legal action while stationed in the other country, and the right to inviolable pouches for carrying their correspondence.

This makes the representatives "official diplomats in everything but name," it said.

"It is common knowledge that as private organizations, [they] have no rights to offer each other the privileges similar to those accorded diplomats. Why could they enjoy these privileges?" the news agency asked.

Twice this year, U.S. Ambassador Leonard Woodcock has been called in by Peking officials because of the Taiwan situation. The first instance was a protest over resumption of U.S. arms sales to Taiwan.

The second involved a formal statement of Peking's attitude on resumption of official relations after Reagan brought the matter up. This was shortly after George Bush's Peking mission failed to clear up Chinese concerns over the Republican presidential candidates' intentions.