President-elect Ronald Reagan's budget advisers have identified enough "waste and fraud" in the federal budget to cut spending by 6 percent, Reagan aide Edwin Meese said yesterday, reviving an old campaign controversy about the accuracy of Reagan's economic projections.

Reagan will "sift and choose" from among the list of possible cuts in meeting his campaign commitment to pare 2 percent from the budget for the current fiscal year, which began last month, said Meese.

So far, neither Reagan nor his advisers have identified in any detail their budget-cutting plan.

Meese's statement surprised a number of Republican and Democratic budget experts, who questioned whether a list of $40 billion in potential reductions -- or about 6 percent of the current budget -- could be found without cutting deeply into politically-sensitive domestic programs or into the Defense Department budget.

President Carter, asked yesterday by reporters to comment on Meese's statement, said he "would doubt its accuracy." Carter ran down a long list of strongly supported programs that could not be cut without new legislation, such as Social Security and veterans' benefits. He noted that if these individual payments programs are immune from budget-cutting, along with defense spending and interest payments on the national debt, then the remaining federal programs would have to be cut by one-third to amass a $40 billion reduction.

During the campaign, Reagan repeatedly promised to cut federal spending by 2 percent in his first year in office by eliminating fraud, waste, abuse and mismanagement -- and without cutting budgets for the Pentagon or major federal aid programs for individuals.

Meese repeated those guidelines yesterday, saying that "rather than cutting whole programs," Reagan's attention would be concentrated on waste and abuse in the budget. Reese added that "there may be some minor programs cuts on that [6 percent] list."

Most budget experts believe that meeting even a 2 percent spending-cut target would be a struggle, under these restrictions.

Several were confounded by Meese's remarks yesterday, made during a press conference on the transition from a Carter administration to a Reagan one. Meese, who is supervising the transition, said Reagan has received a list of possible budget cuts that would amount to 6 percent of the budget, from which the president-elect's final budget decisions will be made.

A 2 percent cut would equal about $13 billion. Casper Weinberger, former budget director in the Nixon administration, and Reagan's chief budget adviser, has said reductions of that size would not be difficult to achieve.

"It's a very modest proposal," Weinberger said recently.

Paul O'Neill, a former top official with the Office of Management and Budget in the Ford administration, and a member of the Reagan task force on spending, said a 2 percent reduction "will take an iron backbone."

The best strategy may be to try to impose some overall spending ceiling throughout the government, rather than single out individual programs, each of which will have its own supporters, O'Neill said.

Congressional budget experts, who do not know what cuts Reagan is planning, have developed their own lists that add up to the 2 percent, $13 billion Reagan campaign target.

To reach that total, however, these lists have had to include some cuts in payments to individuals, such as Trade Adjustment Assistance aid to workers laid off because of import competition, or tightening eligibility requirements for Medicaid and food stamp programs.

Whether these or other reductions in individual payments programs are under consideration by Reagan and his advisers is not yet known.