Energy Secretary James R. Schlesinger singer said yesterday that while there is no immediate problem, Americans should begin voluntarily to reduce oil consumption until production resumes in Iran.

Reiterating other recent cautious assessments by administration officials, Schlesinger said oil shortages caused by Iran's political strife will be "quite manageable" into the summer.

Schlesinger said consumers can help offset the loss of U.S. daily imports of 500,000 barrels of Iranian oil by curbing unnecessary driving, observing the 55 mile-per-hour speed limit and lowering thermostats to 65 degrees.

Such moves, he added, could save the equivalent of 600,000 barrels of oil per day. But he warned that if the Iranian shutoff continues into the fall, the United States would have to use more stringent conservation measures. He termed gasoline rationing unlikely.

He also disclosed that the administration does not intend to propose the removal of price controls from gasoline until after Iran's oil production resumes. Earlier reports indicated a decontrol proposal would be sent to Congress later this month.

Schlesinger also suggested that the Iranian shutoff might encourage new attempts to win congressional approval of legislation taxing U.S. crude oil to raise prices to world price levels.

The voluntary conservation measures outlined by Schlesinger would help minimize the need of the United States and other industrialized nations to "borrow against the future" by using an extra 2 million barrels of oil stockpiled daily.

Schlesinger told a news conference that the loss of oil from Iran, the second-largest exporter, has created a "serious but not critical" world situation.

Iran's exports were stopped last week due to the continuing political strife. Prior to the shutdown, it was exporting about 5.5 million barrels of oil a day, supplying about 5 percent of U.S. imports and 15 percent worldwide.

Schlesinger said that if the shutdown continues into the fall "we will be under conditions of stringency. We and other nations will have to take measures to alleviate this stringency."

Measures could include discouraging the use of motor vehicles, encouraging car pooling, and replacing oil for electrical power generation with coal or nuclear power. Schlesinger mentioned the allocation of available oil supplies to refineries as anothr possible step.

He expressed optimism that oil production will resume when the Iranian political situation stabilizes. "As soon as there is political stability in the country, the Iranian government will be eager to restore production to prevent further deterioration of its financial situation," he said.

He also said the United States will honor its promise, made in 1975, to help Israel obtain oil on the world market or to ship it from the United States. Most of Israel's oil is imported from Iran.

In case of an emergency, he added surplus oil from Alaska's North Slope could be used to help Israel. Congressional approval would be required.