Leaders of the Business Roundable, representing the nation's largest corporations, have formally broken with President Reagan over economic policy, calling for further reductions in federal budget deficits and a slower buildup in defense spending.

The business leaders have decided that the president's budget leaves likely future deficits too high, and thereby increases the risk that interest rates will stay high as well. "Without a sharp drop in interest rates, no reasonable recovery will be seen before the fourth quarter," they said.

They also indicated that the Reagan tax policies should be reconsidered with an eye toward deficit reduction. Reagan has been adamantly against any reduction in the tax cuts scheduled this year and next.

The new position was reached after a reportedly sharp debate Tuesday among some 40 members of the Roundtable's policy committee meeting in New York City. Leading the meeting was Roundtable chairman Clifton C. Garvin Jr., chairman of Exxon Corp.

The co-chairman, Theodore F. Brophy, chairman of General Telephone & Electronics Corp.; James H. Evans, chairman of Union Pacific Corp., and Walter Wriston, chairman of Citibank, were also present.

The Business Roundtable, whose members are the chief executives of 196 major corporations, is the primary lobbying organization for big business. In the past, its members have strongly backed Reagan's economic program and following his State of the Union message in January, Roundtable leaders urged that the Reagan program be given a chance.

Their new policy statement repeated their support for the president's "objectives and basic economic program."

But they said the were "deeply concerned by continued high interest rates and the size of the projected deficits for 1983, 1984 and 1985 and do not believe they are adequately addressed.

"We believe that interest rates and the projected deficits are interrelated," they said, warning that high interest rates will prevent a "reasonable" recovery from the recession until the last three months of this year, much later than Reagan has promised.

"The deficits cannot be addressed adequately without major permanent spending cuts including cuts in the indexed entitlement programs and a slowing of the defense buildup," they added.

Finally, in a terse comment on the debate over tax policy, the Roundtable members said, "it will be necessary to address the revenue side."

A Roundtable spokesman said the policy committee's new position was not issued as a statement. It will be communicated to the White House, however.

The position was endorsed unanimously by the policy committee members following the Tuesday meeting and its wording reflects a consensus of the members' views following a long discussion and debate. "That's as far as we've gone," said one Roundtable source.

The Roundtable members may try to agree on a specific position on tax policy, as that issue develops in Congress, the source said. They were not able to do so at Tuesday's meeting.

Some in Congress want to take back part of last year's business tax cut as one way to raise revenue and reduce the forthcoming deficits.