appreciably after the mid-1960s. The Soviet government began to seek Japanese cooperation in its economic development plans, and the Japanese responded positively. The two countries signed a five-year trade agreement in January 1966 and a civil aviation agreement as well. Economic cooperation expanded rapidly during the 1970s, despite an often strained political relationship. The two economies were complementary, for the Soviet Union needed Japan's capital, technology, and consumer goods, while Japan needed Soviet natural resources, such as oil, gas, coal, iron ore, and timber. By 1979 overall trade had reached US$4.4 billion annually and had made Japan, after the Federal Republic of Germany (West Germany), the Soviet Union's most important nonsocialist trading partner. Japanese-Soviet political relations during the 1970s were characterized by the frequent exchange of high-level visits to explore the possibility of improving bilateral relations and by repeated discussions of a peace treaty, which were abortive because neither side was prepared to yield on the territorial issue. Minister of Foreign Affairs Andrei Gromyko of the Soviet Union visited Tokyo in January 1972—one month before United States President Nixon's historic visit to China—to reopen ministerial-level talks after a six-year lapse. Other high-level talks, including an October 1973 meeting between Prime Minister Tanaka Kakuei and Leonid I. Brezhnev, general secretary of the Communist Party of the Soviet Union, were held in Moscow during the next three years, but the deadlock on the territorial issue continued, and prospects for a settlement dimmed. Moscow began to propose a treaty of friendship and goodwill as an interim step while peace treaty talks were continued. This proposal was firmly rejected by Japan. 1975–1990: Strains on relations After 1975, the Soviet Union began openly to warn that a Japanese peace treaty with China might jeopardize Soviet–Japan relations. In January 1976, Gromyko again visited Tokyo to resume talks on the peace treaty. When the Japanese again refused to budge on the territorial question, Gromyko, according to the Japanese, offered to return two of the Soviet-held island areas—the Habomai Islands and Shikotan—if Japan would sign a treaty of goodwill and cooperation. He also reportedly warned the Japanese, in a reference to China, against "forces which come out against the relaxation of tension and which try to complicate relations between states, including our countries." The signing of the Sino-Japanese peace treaty in mid-1978 was a major setback to Japanese-Soviet relations. Despite Japanese protestations that the treaty's antihegemony clause was