Secretary of Commerce Juanita Kreps said yesterday that "stop-and-go, unpredictable" U.S. government policies are the biggest obstacle to joint energy ventures between American firms and the Soviet Union.

Kreps, speaking to a meeting of the U.S./U.S.S.R. Trade and Economic Council, said the "Carter administration is aware of this problem and is examining the issue along with other impediments to the long-term growth of U.S. Soviet trade."

"American firms have learned the hard way that it is possible to have their plans go awry at the 11th hour. Moreover, it has heretofore proved difficult if not impossible for firms to obtain prior assurance that last-minute disapprovals would not be repeated."

Under the law, the government must approve joint ventures with the Soviet Union, as they must with many other foreign ventures.

Kreps said she understands that business would like to have the same criteria applied to ventures with the U.S.S.R. that are applied to projects with other countries, something she acknowledged "may be too much to ask."

But she said the administration can take steps to alleviate the uncertainty which plagues tries at joint projects between the U.S. and the Soviet Union, especially, but not solely in the energy field.

"If the government is to apply unique criteria to projects with the Soviet Union, it is not too much to ask that those criteria be made known to those corporations preparing to asume the commercial risk, and that they be made known before the fact and explicitly rather than after the fact and by inference."

Kreps, whose prepared remarks were made available here, noted that when joint ventures to develop Soviet energy resources, notably natural gas, were first proposed in 1971, the U.S. was paying $3.3 Billion for energy imports.