In yet another sign of eroding business support for President Reagan, American Stock Exchange President Arthur Levitt Jr. bluntly warned the president yesterday that he must alter his original economic program to reduce crippling deficits and save the nation from "colossal uncertainty."

Levitt told a National Press Club luncheon that "nothing should be sacrosanct" in the president's program except the cut in the personal income tax, and that a bipartisan compromise restraining growth of the deficits has to be reached before June or July to prevent further deterioration in economic conditions.

Except for the United States Chamber of Commerce, virtually every major business lobbying group has now urged President Reagan to modify his economic program.

In response to a question, Levitt expressed a fear that the president has become "wedded to a particular program and is concerned about appearing to vacillate." Levitt, who has met recently with Reagan, said "I am concerned that he is not being flexible to changing economic conditions--the economy is not a static environment."

If the trend toward higher federal deficits is "substantially altered," the Federal Reserve Board "should be ready to accept a moderate increase in the rate of growth in the money supply," Levitt said.

The Wall Street official released an Amex-commissioned poll of brokers and others in the investment community showing that only 41 percent now "strongly approve" of the president's program, against 67 percent a year ago. On the other hand, a majority continues to believe that Reagan's program will "eventually" help the economy.

Adapting stock market jargon, the Amex chairman said that the basic conclusion to be drawn from the poll is that, "While there is not yet a 'run' on Reaganomics, the signals have definitely changed from an enthusiastic 'buy' to something between 'hold' and 'sell.' "

Levitt called for a reduction in the real growth rate for defense spending; a reduction in "entitlement" programs, including Social Security; abandonment of the "rent-a-deduction" part of the business tax program by which some large corporations have been able to escape taxes completely; and imposition of an oil-import fee.

"Washington tends to think of Wall Street as a tiny cell of conspirators secretly manipulating the markets of America to exploit Main Street," he said.

But he said "you cannot argue" with markets, even if you don't like them. Even if wrong, markets "represent what people actually feel, and as such they have to be heard," he said.

Levitt said the message Wall Street was trying to send to Reagan is that he "made a mistake, last fall, in following the extreme treatment prescribed by the supply-siders while abandoning the option of making significant progress toward the basic goal of the budget-balancers."

He had an especially sharp word for Treasury Secretary Donald Regan, former head of Wall Street's biggest brokerage house, Merrill Lynch, Pierce, Fenner & Smith. Asked about a recent Regan comment that blamed high interest rates on Wall Street, Levitt said:

"He's being a good Marine, but when anyone attempts to polarize the situation" between Wall Street and Washington, "he does a disservice. When someone suggests there's a small cabal of people in Wall Street who control the U.S.--well, it isn't true, and he knows better than that."

On monetary policy, 84 percent of those polled in the investment community said the president "should stand behind Federal Reserve Chairman Paul Volcker's policy of monetary restraint." Levitt said Volcker--seated at the head table--"may be the only voice of sanity left in Washington. We respect him for his toughness and his guts."