Chinese leaders forcefully reopened the Taiwan issue in talks last week with Secretary of State George P. Shultz, ruling out any improvement in bilateral ties until the issue of U.S. arms sales to the island is resolved, the official New China News Agency reported tonight.

The report came just hours after Shultz left Peking for South Korea, and it presents a less upbeat assessment of his four-day mission than the secretary gave. Shultz, who previously had said he hoped the Taiwan question would remain in the background during his talks here, declared at his farewell banquet last night that the visit "set the stage for renewed advances built on a stronger foundation of confidence and mutual trust."

But, according to the news agency, Chinese officials told Shultz that until the Taiwan arms sale issue is resolved, any hope of building trust is "out of the question and bilateral relations cannot possibly develop on a sound basis."

The officials, said the agency, also during the talks accused the United States of bad faith in observing the August communique in which Washington pledged to phase out weapons sales to Taiwan while Peking promised to reunite peacefully with the breakaway island.

Officials traveling with Shultz in Seoul were surprised to hear about the statement. They said that no specific detail regarding implementation of the August communique was raised with Shultz by Chinese officials, nor was there any charge that the United States had been violating its terms.

Shultz, in several public statements as well as in the talks, made a point of saying that the United States would keep its commitment to carry out the terms of the August communique.

The criticism reportedly directed at Shultz is the sharpest by Peking since the communique, which Washington had hoped would defuse the Taiwan controversy so the two sides could resume their strategic partnership against the Soviet Union.

In recent months, however, China has carved out an independent foreign policy equidistant between the two superpowers while moving toward normalization with the Kremlin. Political consultations between the two Communist powers resumed in October after a three-year hiatus and the next round is scheduled for March.

The news agency tonight conspicuously cited foreign media reports saying Washington sought to renew its dialogue with China "to exercise some kind of check on the forthcoming Sino-Soviet consultations."

Shultz, in his farewell toast, said his discussions "made important progress in renewing and enriching the dialogue" between Washington and Peking and left him "more convinced of the real opportunities for enhanced cooperation."

The news agency acknowledged that the visit helped "to some extent" to review respective positions on international and bilateral issues. It confirmed that the two nations have parallel interests in ridding Afghanistan of Soviet troops and Cambodia of Vietnamese forces backed by Moscow, said the report.

But, as Chinese leaders reportedly told Shultz, these shared interests cannot push Sino-American relations forward as long as the Taiwan "obstacle" remains..

Shultz repeatedly sidestepped the Taiwan issue in his public statements here, saying only that Washington would uphold its obligations in the August communique.

"The Taiwan issue has been, is, a problem," he said at a news conference yesterday. "We discussed it . . . and I think the most important thing I can say about it is that we have made some commitments with respect to Taiwan and we intend to live by those commitments."

China's leaders, however, told Shultz that the United States has "not strictly observed" the communique's provisions, according to tonight's report.

Specifically, they complained of "distortions" made by unidentified U.S. officials who interpret the agreement as linking the phaseout of U.S. arms supplies with Peking's progress toward "peaceful" reunification of the nationalist-held island with the Communist-ruled mainland.

Peking claims any "prerequisites" would be an unacceptable violation of its sovereignty. In its view, Washington pledged to reduce weapons supplies until they stop altogether without any conditional promises from the Chinese side.

In talks with Shultz, Chinese officials reportedly also protested the opening of a new Taiwan liaison office in Boston and the attendance of national security adviser William P. Clark at a national day reception given by the Taiwan representatives in Washington in October.

When Washington shifted its recognition from Taipei to Peking, it maintained the right to keep "unofficial" ties with Taiwan through a liaison office. But Peking claims a White House adviser's visit to the national day celebration of a rival government exceeds this right to "unofficial" relations as does the opening of new liaison offices.

Finally, Peking reportedly complained to Shultz about the way Washington interprets the communique provision on future arms sales to Taiwan. The United States agreed not to exceed the qualitative or quantitative level of supplies to Taiwan since the 1979 shifting of recognition.

The communique, however, failed to specify whether the quantitative limits would be set by price or volume. If price were the criteria, then the quantity would automatically fall over time through the impact of inflation. If the number of weapons were the controlling factor, Taiwan at least could maintain a current level of supplies without regard to price.

Chinese officials meeting with Shultz protested that the ceiling set by Washington "far exceeded" the monetary value of sales since normalization.

Apparently, they were given reason to believe that volume, not price, would be the criteria.