The National Association of Realtors tiptoed around direct opposition to the main housing aid initiative of Senate Republicans yesterday, choosing instead to throw darts at it from all directions.

The legislation would subsidize mortgage interest rates so that buyers of new homes would pay 4 percentage points below the FHA rate, now 15 1/2 percent, for five years.

The homebuilders association is pushing for the subsidy, which would cost about $1 billion a year for five years, arguing that it is necessary for their industry and to pull the nation's economy as a whole out of recession.

But it doesn't apply to resales of homes, the province of the Realtors.

Rather than out-and-out opposition, however, the Realtors group told the Senate Housing subcommittee yesterday that the bill had a few flaws, ranging from ineffectiveness to expense to abuse of federal power.

The group said the plan would not help many areas of the country because it does not apply to resales, could not be approved fast enough to help housing, provides too great a subsidy and would involve the federal government unnecessarily in housing decisions, contrary to the administration's New Federalism philosophy.

The administration is trying to decide whether to endorse the mortgage interest subsidy bill, and top officials are holding a series of meetings this week to consider the proposal. A Cabinet-level task force is to come up with a recommendation on the bill soon.

The Hill backing for it is formidable. The bill was introduced by Sen. Richard Lugar (R-Ind.), chairman of the Banking subcommittee on housing, and cosponsored by a number of key Republicans such as Sen. Jake Garn of Utah, chairman of the Banking Committee, and Sen. Mark Hatfield of Oregon, chairman of the Appropriations Committee.

But the administration also is wary of the cost, which the homebuilders' economists have been asked to justify in terms of jobs created and economic stimulus.

Meanwhile, Federal Home Loan Bank Board Chairman Richard Pratt told the House Budget Committee that the problems of the nation's thrift industry "continue to mount daily."

The financial burdens of the bank board and the Federal Savings and Loan Insurance Corp., which backs deposits at S&Ls, will "become extremely severe" in the next three years if the current rate of losses continues, Pratt said.