Congress is scheduled to get back to its seemingly interminable task of writing a new farm bill today, with something other than the pain of cutting federal farm spending on its collective mind.

The farm-bill process now appears to be caught in a growing political cross fire -- whether Republicans in the Senate or Democrats in the House will become the first to slash farm spending when the agricultural economy is in a tailspin.

Current farm law is due to expire Sept. 30, but neither the House nor Senate Agriculture committee has finished its respective version of a farm bill and the most difficult part, cutting farm price and income supports, remains to be done.

Beyond the immediate politics, the congressional eye is partially on 1986, with 22 Senate Republicans, including members from such economically afflicted farm states as North and South Dakota, Kansas, Iowa, Indiana, Oklahoma and Wisconsin, will be up for reelection.

Some of those -- Mark Andrews of North Dakota, James Abdnor of South Dakota and Charles E. Grassley of Iowa -- have distanced themselves from the administration's insistence that farm spending be cut. Instead, they are urging more outlays to prop up the rural economy.

But President Reagan and Agriculture Secretary John R. Block repeated their warnings during the congressional recess that budget-busting farm legislation would not be tolerated. And Senate Agriculture Chairman Jesse Helms (R-N.C.) has threatened to become the first committee chairman to vote against a farm bill if it exceeds budget limits.

Enter the Democrats.

Chairman E (Kika) de la Garza (D-Tex.) denied that the delays were purposeful, but his House Agriculture Committee made it clear last week that it doesn't want to wear the black hat first.

Before adjourning in early August, the committee voted to resume work Sept. 4 and to complete action by today. The panel returned last week with no more answers than when it recessed. De la Garza then named a committee to work out a package of farm program cuts to be weighed today.

"Are we really delaying our agony for a few days?" wondered Rep. Steven Gunderson (R-Wis.).

The farm-bill nitty gritty got no discussion. Rep. Pat Roberts (R-Kan.), frustrated by the delays, complained: "The farm bill is being held hostage to a budget process that is a failure . . . . Here we are making speeches again. Let the record show that we are Chicken Littles and that the sky is falling and we have no place else to hide."

The Senate committee, meanwhile, apparently no closer to agreement on farm-support cuts now than it was at adjournment time, plans to resume work today on remaining, less controversial parts before tackling the sensitive money section.

House and Senate committee members continue to wax optimistic that a new farm bill will be ready before the Sept. 30 expiration of current law, but most congressional betting is that they won't make it.

The alternatives are to extend current law while final details of a new program are worked out or to allow the farm programs to revert to a 1949 law that would be both expensive and cumbersome. Either alternative could reflect on Republican leadership.

Or, if the House waits long enough and forces the Republican-controlled Senate to act first and produce a bill that meets the Reagan-Block budget requirements, the GOP gets to wear the black hat in Farm Country.

It is a bind that warms Democratic hearts.