The Soviet Union is ready to pursue "new advanced forms of relations" in its trade ties with the West, Prime Minister Nikolai Ryzhkov said today. The reference was seen here as related to recent Soviet probes toward joint ventures with West European and Japanese firms.

Ryzhkov's remarks, made in a speech before the Supreme Soviet on the 1986-1990 five-year plan, reinforced the view that the Soviets are actively exploring new ways to secure western technology without having to pay for it with a dwindling supply of hard currency.

The sudden drop in the price of oil, which supplies the Soviet Union with about 60 percent of its hard currency revenues, has severely cut back the the country's ability to buy western equipment.

The shortfall in currency also comes at the height of a campaign here to force Soviet industry to upgrade production to world-quality levels. In his speech today, for instance, Ryzhkov noted that only 29 percent of the engineering products made here are up to international standards: by 1990, he said, the percentage should be 80 to 95.

Soviet trade officials this spring raised the prospect of joint venture projects first with Japanese and Scandinavian officials and businessmen, although in each case they left key details unclear. The probes later expanded to other western firms doing business here.

"There have been a lot of serious discussions about joint ventures," said one western diplomat here. "The Russians are talking with anyone that has a sufficient relationship with them, but at the same time, they are still vague about it."

In principle, a joint venture partnership with the Soviet Union would require a major ideological shift for this country, since it suggests that foreign capital, foreign ownership and foreign profits would play a part in the economy of a socialist state.

About two dozen such arrangements are already underway between Soviet enterprises and Eastern European concerns -- in most cases combining Soviet capital and Eastern European technology. The cooperation is in line with the recent policy to integrate the economies of the countries of Comecon, the East Bloc's economic organization.

However, diplomats and businessmen say the Soviet suggestions to western firms, as vague as they are, can be left open to different interpretations, such as the more traditional approach of joint production involving Soviet resources and western equipment.

In some cases, western firms have been asked to come forward with their own proposals on how to get around the problem of partial foreign ownership. Some western businessmen are skeptical about the request, however, which they see as reflecting the confusion and anxiety pervading the Soviet Ministry of Foreign Trade.

While the definition of joint-venture projects remains ill-defined, Ryzhkov's remarks today indicate that the search for new trade relationships is ongoing.

Ryzhkov's report also indicated that the rate of investment, set last February to average 4.6 percent, had been scaled down to 4.3 percent. But the annual growth rate, set last March at 3.7 percent, was increased to 4.1 percent.

Ryzhkov today also renewed Soviet commitment to nuclear power.