A senior Soviet adviser today suggested a conference of European powers to guarantee the West's vital oil supplies in the Persian Gulf.

Nikolai Portugalov, a Communist Party Specialist on West German affairs, said in an official Tass news agency commentary that such a conference could arrive at "proposals for appropriate guarantees" to be "approved by the United Nations."

"The U.N. could expand such guarantees also to the territorial integrity and independence of the oil-producing . . . countries," he wrote.

The specialist also hinted, in what could be a significant sign, that the Soviet Union may itself be a potential buyer of Middle Eastern oil, giving it "a certain parallelism of interests" with other European countries. The CIA has predicted that the Soviets, because of poor exploitation methods, may become net oil importers this decade, a forecast the Soviets have always bitterly attacked.

The commentary continued current Soviet propaganda efforts to draw a clear distinction between the West Europeans and the United States in the Afghanistan and Iranian crises. Portugalov wrote that the Soviet leadership has sketched "initiatives that would offer a favorable alternative to the dangerous development of events provoked in the region by Washington."

In the two months since their Afghanistan invasion, the Soviets have increasingly sought to draw West Europeans into a dialogue at the expense of the United States. The Soviets have also sharply criticized the NATO countries for "mistakenly" agreeing last December to base new strategic missiles on their territory at Washington's behest, and warned them against joining U.S.-led economic and cultural exchange sanctions against the Soviet Union.

Citing U.S. naval forces in the gulf, Portugalov said Washington wants to turn the area into a powder keg "where it could use force at its own discretion." The United States "makes no secret that any internal changes in the oil-producing countries unsuitable to the U.S. may be regarded by it as a pretext for military interference," he said.

The 35 signatories to the 1975 Helsinki accord on European security, which includes the United States and the Soviet Union, could be the appropriate group to meet on securing gulf oil guarantees, he wrote.

"The Soviet Union, far from seeking to force its way to the warm seas, is itself interested in the security of oil supply routes in the gulf," he said. "West German Chancellor [Helmut] Schmidt said in a recent interview the Soviet Union as a potential buyer of Middle Eastern oil has a legitimate right of access to its sources. Thus, a certain parallelism of interests of all European countries is beginning to show."