The breadth and depth of West Germany's long-term involvement in China's modernization program have been highlighted this week by the visit of West German Chancellor Helmut Kohl.
After three days of top-level political meetings in Peking, the chan-cellor has praised China's leaders for ''their farsightedness and their sense of reality.'' Dr. Kohl has also thrown his full political weight behind the efforts of West German industries to gain a share of China's business, thereby sharpening their competitive edge with Western and Japanese rivals.
At a press conference Wednesday night after meeting with China's senior leader, Deng Xiaoping, Chancellor Kohl emphasized the growing friendship between their countries, pointing to the absence of major political problems and even to a congruence of political interests.
''For us Germans, it is of particular significance that a country of the importance of the People's Republic of China ... stands up for German unity,'' he said.
The subject of German unity came up in all his discussions, he added. He also thought the Chinese greatly supported his meeting with East German leader Erich Honecker.
China has unification problems of its own - with Taiwan. It has been quietly encouraging unification talks between North and South Korea. And it has been strengthening its ties to Eastern Europe.
Chancellor Kohl is using his week-long visit to China to demonstrate the kind of personal political support for West German financial cooperation with China that the Chinese value so highly. While no new agreements are expected between the two governments from this visit, Kohl has promised ''financial cooperation'' with China next year. This would probably come in the form of concessional loans and such development assistance as West Germany makes available to other third-world countries.
During the past 12 months, China and West Germany have signed agreements on the protection of foreign investments, the peaceful uses of aerospace technology , and cooperation in nuclear energy. An agreement to protect businesses against double taxation is under negotiation.
Western diplomats expected Kohl's visit to help bids by West German industries for a share of Chinese contracts.
On Wednesday night, the chairman of Volkswagen and his Chinese partners signed a 25-year joint production contract under the watchful eyes of Kohl and Chinese Premier Zhao Ziyang.
The contract calls for production of 20,000 VW Santanas by 1989 and of 100, 000 4-cylinder engines by 1990 at plants near Shanghai. The Santana cars will be sold domestically, while the 80,000 additional engines will be exported to VW plants elsewhere in the world.
The deal apparently means that the French company Automobiles Citroen has lost its bid for an assembly operation in China. American Motors signed a 20 -year contract last year for joint production of its Jeep, which is expected to reach production of 40,000 vehicles a year.
As for nuclear-power plants, Kohl would say only that the subject came up and that discussions were continuing.
China has yet to announce which foreign companies will get the contracts for a $3.5 billion nuclear-power facility proposed for Daya Bay.
Japanese, French, West German, and United States firms are competing for portions of the project. US businessmen here believe China would prefer American nuclear technology. But observers say that with congressional delay in approving the nuclear-cooperation agreement initialed by President Reagan and Premier Zhao last spring, China may end up giving the contracts to the West Germans.
Academic exchanges are also a major link between West Germany and China. With 1,100 Chinese students studying there, West Germany has the third-largest number of Chinese students studying abroad, after the US and Japan.
Kohl and his party have met with President Li Xiannian, Communist Party Secretary Hu Yaobang, Foreign Minister Wu Xueqian, Zhao, Deng, and other top officials. Both sides said they were pleased with the discussions.
Kohl said that Deng and others spoke freely about their personal difficulties during the Cultural Revolution (1966-76) and that this was evidence that the Chinese leadership will not go back on its policies.
These policies include fundamental economic reforms and opening to foreign trade and investment. He said he was convinced their ''path is irreversible.''
Zhao has accepted Kohl's invitation to visit West Germany next year.