The budget resolution passed by the House proposing cuts of $35 billion in President Reagan's defense budget will force cancellations of a string of weapons to achieve the savings, Pentagon and congressional leaders agreed yesterday.

Although the Pentagon has predicted dire consequences throughout the five-year-old Reagan rearmament program, they did not materialize when reductions were imposed by Congress. But this year will be different, according to Chairman Les Aspin (D-Wis.) of the House Armed Services Committee, and to Deputy Defense Secretary William H. Taft IV. Both said yesterday there are no easy ways left to absorb the prospective reductions.

Taft, while stressing he did not favor the cuts, said that big-ticket items such as the Air Force C17 transport and the Army LHX helicopter will have to be scrapped to achieve the savings over the next three years recommended by the House and Senate. The House budget resolution cut of $35 billion and the Senate reduction of $19 billion would be from Reagan's fiscal 1987 request of $320 billion.

Aspin urged the House to consider reducing military commitments abroad rather than go through with the cancellations and stretchouts needed to achieve the savings called for in the budget resolutions. These were designed to reduce the federal deficit and avoid triggering budget reduction mechanisms contained in the Gramm-Rudman-Hollings legislation.

Since the administration has no intention of pulling back from military deployments in Europe, the Persian Gulf or the Pacific, Taft said, savings could not be achieved this way. Therefore, he predicted, budget cutters will have to cancel and stretch out most of the programs on the hit list the Pentagon submitted to Congress last week. Another item on the big-ticket list besides the C17 and LHX is the Navy's advanced version of its A6 bomber.

"Congress is just about out of wiggle room" in trying to avoid politically explosive weapons cancellations by resorting to stretching out programs, said a Pentagon budget executive yesterday. Cancellations will have to be even more numerous next year to reach House and Senate budget targets for the Pentagon, he said.

Aspin said Congress could carve about $25 billion out of Reagan's budget request of $320 billion by doing the trimming the old way -- "stretching out weapons, deferring much construction, stripping out inflationary padding and reestimating costs.

"Once we go below that point," he said, "the wolf begins to materialize. The good news is that it should force Congress into making policy decisions and really framing national defense policy for a change. The bad news is that we'll have to produce the kinds of cuts that many members will find unattractive."

Aspin, in a 14-page analysis, laid out a series of options "designed to illustrate how you could give some strategic coherence to budgeting." They included obtaining money to keep current forces ready to fight with present-day weaponry by canceling programs just getting started, such as the C17 transport plane, and the Bradley Fighting Vehicle and slashing research accounts by one-third. He estimated this would save $54 billion in budget authority -- the money put in the bank for the Pentagon and paid out over a number of years -- but only $10 billion in actual spending in fiscal 1987.

Other options, Aspin said without endorsing any of them, would be to cancel such strategic programs as the Air Force MX and Navy Trident D5 missiles to free money for conventional forces; abandon Persian Gulf commitments, allowing the Army to dispense with two light divisions, reduce U.S. forces in Europe and depend more heavily on reserve forces by deactivating two Army divisions, three Air Force wings and 57 Navy ships.

Taft, in an interview in his Pentagon office, said if the House's recommended $35 billion reduction is implemented "you're not going to find Les Aspin or the Senate Armed Services Committee or any of these committees coming up with any more than five to ten billion" in reductions that are not already on the Pentagon list submitted to Congress last week.

Both Congress and the Pentagon have been reluctant to cancel weapons in the first five years of Reagan's military buildup. The scrapping of the Army's Divad (Division Air Defense) gun was one of the few exceptions. But now, according to Pentagon and congressional budget analysts, there is not enough money in sight to finish what Reagan has started.