China is sending its ranking military officer and a leading government official on separate trips to the United States.

The official New China News Agency announced tonight the departure of Yang Dezhi, chief of the general staff of the People's Liberation Army. His trip is seen as the latest evidence of strengthening military ties between the two countries. No previous holder of the post has made a U.S. visit.

Gen. Yang was a deputy commander of the Chinese forces fighting the Americans in the 1950-53 Korean War.

The civilian, senior Vice Premier Yao Yilin, also will be making his first trip to the United States, diplomats said today. Both are to stay about two weeks. Yao plans to leave here in mid-May.

U.S. officials are expected to use Yao's visit to try to resolve problems that have slowed American business investment in China.

Yao is to meet in Washington with Commerce Secretary Malcolm Baldridge and to head China's delegation to the fourth annual session of a joint commission on trade.

An American dealing with projects here said Baldridge is likely to raise the concerns of American businessmen working in China over the shortage of foreign exchange, difficulty of repatriating profits, and rising costs of doing business.

Secretary of the Treasury James Baker III is expected to discuss the same issues on a visit here following the Tokyo economic summit.

Neither Yao nor Yang has been associated until recently with moves to strengthen U.S.-Chinese relations. Yao is considered "conservative" by many foreign specialists. He once worked closely with Chen Yun, the senior economic planner who has criticized some of the side effects of the policy of opening China to more foreign trade and investment.

Last July, Yao signed a five-year, $14 billion trade agreement with the Soviet Union, thus significantly expanding trade with that country.

But Yao, who is a specialist in trade, economics and finance, has shown repeatedly that he can listen to the criticism of foreigners without taking offense. A European who has met with him twice said that Yao is open to new ideas when it comes to reforming China's aging state-run industries.

Yao will have a chance to brief U.S. officials on China's renewed ties with the Soviet Union in the fields of trade, culture, and education. A diplomat said Yao may also want to raise objections to U.S. policy on Taiwan.

Yang is expected to meet with top U.S. military leaders and visit Army installations.

In an interview with the China Daily newspaper published yesterday, Yang said his visit was "not directed against a third country." He was taken to mean the Soviet Union.