Sen. John H. Glenn (D-Ohio) yesterday expressed concern about President Carter's failure to obtain a clearcut pledge from China not to use force against Taiwan, and warned that peaceful settlement of the Taiwan issue "must be the immediate guiding principle" of U.S. dealings with China.

Glenn's warning could be of major significance in the upcoming congressional debate over the administration's China policy. As chairman of the Senate Foreign Relations subcommittee on East Asia, he is one of the influential Senate moderates whose backing the administration wants to counter conservative attacks on the decision to establish relations with China.

Glenn visited China earlier this month, and his detailed report on the trip is scheduled to be made public today. In the report, he is generally supportive of Carter's decision to recognize Peking, and calls normalization of relations "a crucial step in U.S. for eign policy."

But, in comments yesterday, he said his concern about Taiwan's security had been heightened by his talks with Chinese interpretations of their understanding over Taiwan.

He pointed out that, when the agreements were jointly announced last month, Carter said the United States recognizes Peking as the sole legal government of China and "acknowledges" Peking's claim to Taiwan.

However, Glenn added, the Chinese government's parallel statement does not use the Chinese work for "acknowledge," and is phrased instead to say that the United States "recognizes" China's claim to Taiwan.

Glenn criticized the administration's failure to protest the Chinese use of words, and warned that he will make "that issue and the security of Taiwan my principal focus of interest" when the Senate Foreign Relations Committee holds hearings Feb. 5 and 6 on administration plans for putting U.S. ties with Taiwan on a nongovernmental basis.

"The security of Taiwan must be maintained," he said. "Because of this confusion, there may be a need for legislation clarifying whether the laws of the People's Republic of China apply to Taiwan."

In his report to the Foreign Relations Committee, Glenn discusses in detail China's economic situation, foreign policy, internal politics and military strength. Among the report's conclusions:

Trade. Although normalization should lead to increases in U.S. trade with China, the growth will be gradual, and "it is important not to overestimate the benefits that can flow from this new relationship."

U.S. relations with the Soviet Union. "Having established a triangular diplomatic balance between China, the Soviet Union and the United States, we must be careful not to 'tilt' toward either communist power."

Korea. The United States should "pursue reduction of tensions on the Korean peninsula with the Chinese.... Assuming that the Taiwan issue is left for peaceful resolution, it seems to me that Chinese cooperation in reducing the tensions of the Korean peninsula becomes the acid test of future Sino-American relations."