Congress `must' list likely to delay end of current session. UNFINISHED BUSINESS

Officially, Congress will wrap up its work for this year and leave town Nov. 21. Unofficially, no one believes that is going to happen.

Lawmakers, looking ahead to next year's pivotal election season, are eager to get out and get campaigning as soon as they can. This is especially true for the five members of Congress now running for president.

But first, the House and Senate have to clear a few odds and ends out of the way. Among them:

The budget. This week, congressional leaders and administration officials began searching for a compromise plan to carve at least $23 billion out of the federal deficit. If there is no agreement, the automatic budget-cutting mechanism established by the Gramm-Rudman deficit-reduction act will do the chopping for them on Nov. 20.

Meanwhile, Congress must pass a tax-raising, budget-trimming reconciliation bill, as well as 6 of 13 appropriations bills that fund almost every federal program. (Work on the other seven has been finished, but Congress has yet to send them to the President for his signature). If this year follows in the path of the last few years, those 13 appropriations bills will be rolled into a legislative behemoth called a ``continuing resolution'' - more than a half-trillion dollars' worth of federal spending commitments that must be signed by President Reagan if the federal government is to keep its doors open.

The Nicaraguan contras. Whether the peace accord signed by the five Central American presidents succeeds or fails, the Reagan administration says it will ask Congress to approve an additional $270 million in aid to the Nicaraguan rebels, better known as the contras. The terms of the accord must be met by Nov. 7 - an admittedly tall order, considering that it calls for a halt to all outside military aid to the region's various rebel factions, a negotiated cease-fire between all combatants, and the implementation of democratic reforms by Nicaragua's Marxist Sandinista government.

Costa Rican President Oscar Arias Sanchez, who has been awarded this year's Nobel Peace Prize for his choreography of the peace effort, has promised that he will formally announce the accord's success or failure shortly after the Nov. 7 deadline. Regardless, Secretary of State George Shultz has told Congress that the administration will press for a vote on its contra-aid package before Thanksgiving. Both sides are gearing for what one pro-contra lobbyists predicts will be a ``battle royal.''

The Supreme Court. Today, the White House is expected to announce a new nominee to replace retired Associate Justice Lewis Powell Jr. on the Supreme Court. The new nominee will likely share the conservative philosophy of Judge Robert Bork, recently rejected by the Senate, while not being as controversial. For example, the new nominee is not likely to have left the trail of controversial papers and speeches that, in part, led to Judge Bork's rejection.

White House chief of staff Howard Baker Jr. and Attorney General Edwin Meese III have been testing the reaction of Senate Democrats and Republicans to individual names. But that does not necessarily mean the administration will choose a candidate to the Senate's liking.

Senate Judiciary Committee chairman Joseph Biden (D) of Delaware says there is virtually no chance that the Senate will finish with the new nominee by Thanksgiving. Senate minority leader Robert Dole (R) of Kansas predicts that the Senate will dispense with the next nomination just shy of Christmas.

Agriculture. The Farm Credit System used to be the pride of the American agricultural establishment. Its banks provided loans to family farmers who owned and ran their own agricultural lending cooperatives. They paid the government back its money and turned a respectable profit at the same time. Now the system is sagging with the rest of the US farm economy.

By 1989, it stands to lose nearly $8 billion. Farm credit officials say that unless Congress comes up with at least $6 billion, the system will go under - pulling a sizable chunk of the US economy down with it. After extended and sometimes agonizing effort, Congress appears set to pass legislation to reform as well as replenish the system.

The environment. For the last seven years, Congress has been deadlocked over the reauthorization and overhaul of the Clean Air Act, a landmark 1970 statute that imposes air-quality standards nationwide. The act expired in 1981, though hastily cobbled extensions have kept it alive ever since. After six years of extensions, the act badly needs to be updated.

Meanwhile, environmentalists and industry are at war over what new pollution controls should be incorporated into the act, while lawmakers representing the Northeast and those hailing from the Midwest are fighting over what steps the act would take to control acid rain. No version of the bill has been permitted onto the floor in either chamber.

On Dec. 31, the act says, cities and counties must meet strict standards for controlling levels of ozone and carbon monoxide in the air or face the loss of federal grants and a ban on construction of certain new industrial plants. Lawmakers are working to find agreement on an extension of the deadline.