Nuclear freeze -- what would the message be?

A powerful sentiment growing up through the grass roots of the country will almost certainly force the US House of Representatives to approve a nuclear weapons freeze.

But 13 hours of contentious debate on the House floor Wednesday and postponement of final passage until next month shows that Congress still hesitates before trying to taking a firmer hand in setting foreign policy.

House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts calls the freeze resolution an ''easy vote'' for members, since there's ''nothing that binds Congress.'' Far from requiring an immediate halt in the weapons buildup, the measure states that the United States and USSR should seek an ''immediate, mutual, and verifiable freeze.''

The freeze resolution would nudge the Reagan administration to change its negotiating strategy at arms talks with the Soviets. It would also challenge priorities in the White House, which has called for spending $1.7 billion for defense, including major new atomic weapons, during the next five years.

Despite its nonbinding nature, the freeze resolution has stirred a controversy that will probably still be sending sparks well into the 1984 election campaigns. For supporters, it is a first step toward removing the nuclear threat that hangs over the world. Opponents warn it will take away the President's bargaining chips at the negotiating table and weaken the nation's security.

The practical results of a freeze resolution, which narrowly lost in the House last year, are difficult to measure.

House minority leader Robert H. Michel of Illinois warns that the freeze is a prelude to slashing funds for nuclear weapons. ''That's unilateral disarmament, '' the Republican leader says. But Speaker O'Neill argues that Congress will not reject nuclear weapons if it approves a freeze resolution. In fact, the Speaker says he sees growing support even for the MX missile, probably the most vulnerable weapon system.

Rep. Les Aspin (D) of Wisconsin said that he and many other members will vote both for the freeze and for nuclear arms.

''Weapons systems are always hard to cut,'' he said, since they provide jobs to constituents and represent a safe, ''patriotic'' vote.

''So I think Congress will cut the (defense) budget, but it will not cut weapons systems,'' said Representative Aspin, explaining that he will oppose the B-1 bomber, but only because he considers it wasteful. ''I think you ought to vote for or against weapons based on whether they are good for defense, not on the basis of the freeze.''

Also at stake in the debate is the US position on arms negotiations. Lawmakers usually allow the President to conduct foreign policy. But many in both parties are feeling the heat from voters who want faster action on arms control.

Rep. Edward J. Markey (D) of Massachusetts, a prime sponsor of the nuclear freeze in the House, predicted this week that the freeze will win because ''a lot of people who voted against the freeze'' last year lost in the elections. Republican leader Michel concedes that the issue hurt some GOP candidates.

Presidential candidates are clearly taking the cue. All five Democratic senators who are either officially or unofficially running for president have signed on to the freeze proposal. And former Vice-President Walter Mondale has been an outspoken proponent.

In the House, a broad coalition from both parties favor the freeze as a ''message'' to the President that they want arms control pushed to the front burner.

While Reagan has used the US nuclear buildup as a lever to force the Soviets to negotiate, the freeze takes the opposite tack. It calls on President Reagan first to seek an agreement with the Soviets to stop building nuclear weapons and then negotiate for reducing arms.

Opponents not only argue that the freeze would not be verifiable, but the administration says the freeze would make arms negotiations ''immensely more difficult'' since ''the Soviets would have no incentive to negotiate.''

The measure still faces an uphill battle in the Senate.