The five major domestic automakers' U.S. car sales rose 7.2 percent in early May from their level for the same period last year, with Chrysler Corp. and Ford Motor Co. showing the largest gains, the auto companies reported in Detroit yesterday.

They said they sold 135,323 cars in the May 1-10 period, compared with 141,990 one year earlier. But the 1980 period had one more selling day, and the percentage comparison is based on the rate of sales per day.

According to Arvid Jouppi, a Detroit-based auto industry analyst for John Muir & Co., automakers' sales remain "unsatisfactory" despite the improvement.

"They are measured against the Mary performance a year ago when the sales reached their lowest ebb since the boom ended in March 1979," Jouppi said. "To be 7 percent ahead of that is not at all satisfactory."

He said interest rates, which have been increasing in recent weeks, "are proving to be every effective in delaying automobile sales."

Meanwhile, Transportation Secretary Drew Lewis told a House panel here yesterday that the nation's economic problems could delay recovery of the auto industry for several years beyond the 1985 target date.

"The economic situation is much serious than anybody thought," Lewis said as a Transportation subcommittee opened two days of hearings on the auto industry.

"Instead of being completed in 1985, it may be 1986 or 1987 before it [auto industry recover] is completed," Lewis said.

Rep. John Burton (D-Calif.) questioned Lewis on what he said was a $10 billion shortfall between what will be provided by the Reagan administration's proposals to help the auto industry and what the industry needs to remodernize and retool to complete with fuel-efficient imports.

"Where is that [$10 billion] coming from?" Burton asked.

Lewis said there might have to be some modifications in the plan, such as sale of assets by auto companies, and a stretch-out of the time it will take the industry to "close the gap."

He said the Reagan economic program was the "cornerstone" of the plan for the auto industry.

"No matter what you [Congress] do, until we get the economy under control . . . until we get interest rates under control, it won't help the auto industry," Lewis said.

In answer to a question from Rep. Hal Daub (R-Neb.) as to what the U.S. auto industry will look like in three years, Lewis said it will survive, but he envisions a "no-growth industry, a small-car industry," a much smallerf industry than it used to be.

"No matter what we do to improve the industry, it will still have 400,000 unemployed," he said.

And in Brussels, U.S. Commerce Secretary Malcolm Baldrige rejected European Common Market criticism of the United States' agreement with Japan over auto exports and said it did not run counter to the principles of an open world market.

Following two days of talks with top EEC officials, Baldrige told a press conference that the accord signed earlier this month was "not a step backward for free trade."

He said the three-year agreement had been necessary to prevent the passage of legislation in the United States unilaterally setting quotas for importing Japanese-built autos, which would have constituted a "serious obstacle" to free trade.

Chrysler said it sold 15,662 cars in the first 10 days of May, up 38.9 percent from 12,694 in 1980; Ford announced sales of 33,356 cars, up 22 1/2 percent from 30,638 a year earlier; General Motors Corp.'s sales fell 2.3 percent in the period to 79,600 from 91,695 last year; and Volkswagen of American reported a 14.4 percent drop in sales to 2,605 cars from 3,425.

Sales by American Motors Corp. was estimated at 4,100 cars, a 30 1/2 percent improvement from 3,538 in the 1980 period. AMC's 10-day sales must be estimated because the company reports its results on a monthly basis only.

AMC's 10 percent rebates were the only rebates offered by U.S. automakers during the period.

For the year so far, auto industry sales are down 3.4 percent to 2.40 million from 2.53 million a year ago. There were two more selling says in the Jan. 1-May 10 period last year, so again the comparisons are based on sales per day.

Chrysler is the only automaker with improved sales for the year to date, at 299,134 cars, up 22.4 percent from 248,901 at the same point in 1980. However, Chrysler's sale were extremely weak a year ago as the troubled automaker headed for a record annual loss of $1.71 billion.

Ford's sales of 534,791 cars for the year are down 4.9 percent from 572,706 last year; GM's sales are off 6.6 percent to 1.45 million from 1.58 million; VW's sales of 60,465 cars are down 10.9 percent from 69,125 last year and AMC sales are down an estimated 4.7 percent to 55,800 from 59,521.