President Reagan and Premier Zhao Ziyang, in an exchange of letters commemorating the 10th anniversary of the Shanghai Communique, have acknowledged the current disagreements between the United States and China but expressed willingness to overcome them.

The letters, made public by the State Department, were dated Feb. 28. U.S. officials said Reagan's letter was sent Friday and Zhao's reply received over the weekend. The language in both letters was notably cautious and restrained, especially in view of the nature of the occasion, with Zhao's statements closely following those of Reagan in substance and tone.

As part of his letter to the Chinese premier, Reagan reaffirmed the U.S. positions in the Shanghai Communique of 1972 and the joint communique establishing full diplomatic relations in 1978. He went on to express "willingness" to work with Peking "to overcome differences" and deepen Sino-American ties.

Zhao replied that he believes ties will continue to develop so long as both governments adhere to "the principles jointly established" in the two documents and "overcome the obstacles currently existing" in the relationship. He said the Chinese side "is willing to make efforts" with Washington to this end.

The letters did not mention Taiwan by name, but Peking's New China News Agency sharply criticized U.S. plans to continue selling arms to Taiwan. As quoted by United Press International, the Chinese commentary said "Sino-U.S. relations will retrogress" if the U.S. insists on a long-term policy of selling such arms.