China has signated its concern over the future of Eastern Europe and relations with the Soviet Union with an unusual message to the Yugoslav Communist Party Congress and a reported decision by Chairman Hua Kuo-feng to make an unprecedented trip to Yugoslavia and Romania.

Peking's latest moves to strengthen ties with the two East European states reflect both Chinese uncertainty about what will follow the death of Yugoslavia's President Tito and also China's deteriorating relations with Albania, formerly its closest European ally.

Western news agencies in Belgrade say high Yugoslav party sources have confirmed Hua's plan to visit Belgrade and Bucharest in August, although Peking has said nothing about the trip so far. It would be the first time a chairman of the Chinese Communist party has traveled west of Moscow, the destination of the late Chairman Mao Tse-tung's only two trips outside China.

The Chinese Communist Party broke relations with its Yugoslav counterpart more than 20 years ago when Belgrade rejected Stalinism and began to experiment with economic measures considered too unorthodox by the Chinese. State-to-state relations warmed in more recent years, however, as Peking joined Belgrade in turning against the domineering Soviets.

Tito's visit to Peking last year brought signs of a return to party relations. A warm message last week from the Chinese Central Committee to Yugoslavia's 11th Congress of the League of Communists, Belgrade's reigning party assembly, appears to signal the complete healing of the old spilt.

The Chinese even seem to be interested in borrowing of some of the Yugoslav's capitalist-tinged industrial medthods. Yugoslav journalists have reported Chinese experiments with Belgrade's system of ad hoc price and product decisions by individual factories. The Chinese have said little about this device, which could rupture Peking's tight contols on inflation.

Tito, 85, was healthy enough to address the Belgrade congress and his potential successors are likely to do what Peking fears most - move Yugoslavia back into the Soviet camp. But Hua and the rest of the Chinese leadership apparently want to do what they can now to cultivate those who will take Tito's place.

The Albanians have reacted with muted anger to Peking's growing ties with Yugoslavia, its not always friendly neighbor. They have also objected to China's new ties with United States, preferring the old days when Albanians and Chinese joined together to denounce both superpowers with equal harshness.

Albania launched another salvo in Peking's direction Saturday with an article that appears to back Vietnam in its better feud with China over treatment of overseas Chinese.

"No one has the right to exert pressures and threats" against Vietnam, said the official Albanian party newspaper Zeri i Popullit. Although it did not name China, the newspaper printed its commentary just as Peking was harshly criticizing Hanoi for delaying a planned sea evacuation of ethnic Chinese from Vietnam.

The Chinese particularly value Tito's infuence as one of the founders and most infuential voices in the nonaligned nations movement. Peking has been railing against the Cubans for their military involvement in Africa on behalf of Moscow. The Chinese want Cuba kicked out of the nonaligned movement for being too close to Moscow, thus directing a blow against Soviet influence in the Third World.

Tito has not publicly endorsed that course, but he and his assistants have spoken out against efforts to "reorient" the nonaligned movement so that it opposes only the West, and not the Soviet block. Peking's official news agency has enthusiastically reprinted many of those statements.

Hua's trip to Eastern Europe would be only his second known journey outside China, after a visit to North Korea earlier this year. Some observers here feel willingness to travel so far indicates that Hua feels secure with leadership partners such as Vice Chairman Teng Hsiao-ping, despite signs that Hua and Teng disagree on some key domestic issues.