A group of high-powered American defense industry executives completed an unpublicized week-long visit to Peking today as part of an "exploratory mission" to learn more about China's defense industry and its needs.

The visit was the first of its kind to China and appeared to point toward further defense cooperation between the United States and China. It followed a recent decision in Washington to make the first offer of a government military sale to China. The sale would include technology and equipment to modernize China's production of artillery ammunition.

Roger W. Sullivan, the delegation leader and executive vice president of the National Council for U.S.-China Trade, said the executives were "not here to sell weapons but to begin a process of discussion and familiarization, which will in all probability lead not only to sales but also to some form of cooperative ventures in the defense areas."

Sullivan said the group of 18 executives from major U.S. companies such as Boeing, Ford, Honeywell, Hughes Aircraft, Lockheed, Martin Marietta, and Rockwell International, were well received by the Chinese and are being given considerable access to defense factories. Group members have visited electronics factories and an armored vehicle factory, and will see aircraft and shipbuilding factories.

The group, which will travel outside Peking for another week, left the Chinese capital today for Xian, a center for aircraft production.

The business executives' visit has gone unreported so far by the Chinese press. China maintains an independent foreign policy posture and does not like to give the impression that it leans toward either the United States or the Soviet Union. Defense sales are a sensitive issue for China; both the Chinese and the Americans have been proceeding at a deliberate pace in this area.

Despite the apparent reluctance of some elements in the traditionally conservative Chinese military to accept foreign cooperation, the U.S. business leaders were given red-carpet treatment and stayed at the state guest house.

The group's host organization during their visit here has been the New Era Corporation, which is the commercial arm of the Chinese Commission of Science, Technology and Industry for National Defense.

Asked about the purpose of the group's visit here, Sullivan said, "It's long been an assumption of U.S. policy, going back to vice president Mondale's visit here in September 1979, that a normalization of defense relations was an integral part of the whole process of normalization.

"We've now reached the stage in the development of that relationship on a government-to-government basis when it's time to explore what this cooperation would mean in practical terms and what it would mean for private industry in the United States."

The National Council for U.S.-China Trade, which organized the executives' trip to China, is a nonprofit organization based in Washington that promotes trade between the United States and China.