A Senate Republican leadership effort to force a floor vote on part of a farm bill before the August recess collapsed last night in a gush of blame-laying and backing down.

Majority Leader Robert J. Dole (R-Kan.) has threatened to bypass the Agriculture Committee, where the legislation was caught in a tangle, and call up a bill of his own for floor debate.

Dole had argued, and committee Chairman Jesse Helms (R-N.C.) agreed, that the committee was so hopelessly deadlocked that he had no alternative.

But faced with a potentially embarrassing floor donnybrook, Dole suddenly dropped the threat last night and announced that the Senate would devote two hours today to a "discussion" of budget implications of various pending farm-bill proposals.

Democrats, ready to object to Dole's floor gambit, contended that they were prepared to vote in committee on a crucial and controversial price-support section of the bill but that the GOP leadership was fearful of the outcome.

The panel argued over the support section most of the morning, but a scheduled afternoon session, when an agreement might have been worked out, was canceled when Helms said he had another commitment.

Democrats then took to the Senate floor to denounce the Dole plan to bypass the committee and to accuse Republicans of sacrificing farm income supports to meet vague budgetary guidelines.

Sen. Alan J. Dixon (D-Ill.) argued that the Agriculture Committee had completed "95 percent" of its work and was no more than one meeting away from finishing.

"I've never seen us abandon the committee process when a bill is almost completed," he told the Senate. "I don't understand what is going on here . . . . I don't know why we bring up a bill [on the floor] and grandstand for the public at large."

The centerpiece of the income-support dispute involved the timing and amount of direct subsidy payments to farmers. Last week, the committee voted 9 to 8 for a Democratic-proposed four-year freeze that would keep the payments at current levels -- which would have added more than $4 billion to the cost of the bill.

The measure pending before the panel, supported by Dole and Helms, called for a one-year freeze with reductions in later years. Helms was defeated yesterday, on another 9-to-8 vote, when he offered a compromise two-year freeze.

But Dole then prevailed, 9 to 8, with a variation of the two-year freeze, amid a welter of confusion in which Sen. Edward Zorinsky (D-Neb.) changed his vote twice.

The committee quit for the morning with Sen. John Melcher (D-Mont.), original author of the four-year freeze, trying to amend the Dole bill back to four years.

Dole, who earlier announced he had "about given up" on the committee, told the Senate later that he was ready to call up a bill for a floor vote and that he was prepared to file a cloture petition to cut off debate if necessary.

The majority leader and his allies had argued for days that a floor vote was vital for farmers nearing winter wheat planting time, who needed to have an idea of the shape of the farm program under which they would be operating.

The House Agriculture Committee, meanwhile, continued in similar but less controversial deadlock yesterday over the wheat and feed grain price-support sections of its farm bill.

A scheduled reconsideration vote on a program adopted last week was postponed as committee leaders looked for ways to forge stronger consensus among members sharply divided over income-support approaches.

Rep. Thomas S. Foley (D-Wash.), architect of the approved price-support plan, agreed yesterday to modify it by giving the secretary of agriculture the choice of another plan, which also was rejected earlier. But Rep. Berkley W. Bedell (D-Iowa), reflecting the unhappiness, called the modification "a farce."