Farm-state Democrats reached for the initiative yesterday in the farm-debt assistance debate, announcing that the House leadership has promised early action on a bill that could make billions of extra dollars available to farmers before spring planting without increasing the federal deficit.

Rep. Thomas A. Daschle (D-S.D.), chief sponsor, said that his bill has been given "fast-track" status by the Democratic leadership and that he thought it could be passed and sent to the Senate by the end of the month.

Several farm-state senators have indicated that they would support legislative relief for farmers. But the Reagan administration strongly opposes such a step, saying that the debt restructuring program it announced this week is adequate.

Daschle said his proposal met three basic standards: It would not increase budget costs, it is the most direct thing Congress can do, and it will assist more farmers than would the administration's heavily criticized program.

The bill, whose 15 cosponsors include House Majority Whip Thomas S. Foley (D-Wash.), would give farmers immediate advances on crop loans that they ordinarily would not receive until harvest. It also would change several key provisions of the Reagan program.

Daschle's loan-advance idea could get billions of dollars to farmers to help them pay planting costs and to bring other debts current. Each farmer would be eligible for a 50 percent advance on his 1985 crop loan and would be charged 9 1/2 percent interest until the crop is harvested.

Another major provision, supported by commercial bankers and officers of the independent Farm Credit Administration, would broaden the eligibility standard for participation in the guaranteed-loan portion of Reagan's program.

Without the change, bankers said, they would shun participation.

The president's plan, announced before the November election and then revised last week at the urging of farm-state legislators, provides federal guarantees for private loans and allows the Farmers Home Administration to delay collection of 25 percent of a farmer's loan, without interest, for five years.

The new program has been criticized roundly by bankers, farm groups and members of Congress, who charged that it will not be enough to prevent a worsening of the credit crisis that has threatened thousands of farmers with bankruptcy this spring.

"My concern is that what we're doing is not enough," Daschle said. "At our House Agriculture subcommittee hearing Thursday on the credit situation, every witness who was asked gave the administration's debt assistance package a 3 on a scale of 10. If no one thinks it is good, it won't be used, no matter how adequate the administration thinks it is."

"The farm economic situation is getting worse by the moment in South Dakota. We have lost 2,000 farmers in the last 18 months; some estimates are that we could lose 3,000 more this year . . . I fear we could have an economic collapse in the next 18 months that could make the Depression look like a picnic," Daschle said.

Other legislators from the major grain-producing states of the Midwest have echoed Daschle's fears, with some forecasts indicating bankruptcy or failure for as many as 15 percent of the region's farmers this year.

The credit crisis continued yesterday to stir emotions in the heartland. In Minnesota, a task force chaired by Gov. Rudy Perpich agreed unanimously that the state should seek a federal economic emergency declaration in 69 of Minnesota's 87 counties.

Plans were announced for a "National Crisis Action Rally" on Feb. 27 in Ames, Iowa, with a sponsoring coalition of farm groups issuing a call for Reagan to attend and meet with the 35,000 farmers they hope to draw. Another rally at Pierre, S.D., is expected to draw thousands next Tuesday.

In Illinois, officials of the American Agriculture Movement, which sponsored the protest tractorcade to Washington in 1979, announced that they would mount another "Farmers' Parity March" on the capital March 4-8.