Washington area police warned commuters yesterday to expect heavy traffic and delays on Monday morning because of protesting farmers who plan to drive more than 2,000 tractors and other farm vehicles into the District.

About 1,300 farmers have been staying in the parks in Fairfax County since Wednesday night, and yesterday a third caravan of about 800 vehicles stopped at a farm outside Frederick, Md., 40 miles northwest of Washington.

Leaders of the farmers' American Agriculture Movement said yesterday four tractorcades will converge on Washington during the Monday morning rush hour, and then move through the city toward the Capitol. The farmers said they plan to return to their campsites during the evening traffic rush and repeat their parades every day until their goals, higher farm prices, are met by Congress.

D.C. police yesterday advised commuters to use public transportation and to join carpools Monday. Fairfax County police said that Northern Virginians who usually use the interstate system should take alternating routes, if possible.

In Virginia, police said one tractorcade will be coming from Bull Run Park in western Fairfax on Interstate 66 and then merging into the eastbound lanes of the Capitol Beltway.

A second tractorcade, coming from Pohick Bay Regional Park, will cross Rte. 1, traveling west on Lorton Road to 1-95, police said.

The farmers plan to merge these two tractorcades into the Shirley Highway express lanes near Springfield, which will be closed to other traffic in the early morning, police said. The farmers will go into Washington over the 14th Street bridge and up Independence Avenue to the Capitol.

In Maryland, farmers spending the weekend near Frederick plan to bring about 800 tractors south on Interstate Rte. 270 to the beltway. The caravan will head west to Canal Road, according to the U.S. Park Police. It will take the Whitehurst Freeway to Virginia Avenue, and go up Constitution Avenue to the Capitol, Park Police said.

Another smaller caravan of farmers, with about 50 tractors, plans to come into Washington from Maryland on Rte. 50 to New York Avenue, taking North Capitol Street to the Capitol, police said.

Gerald McCathern, national wagonmaster of the farmers' tractorcade, said it will probably take about four hours for the farmers to get from the park to the Capitol.

Several farmers yesterday responded to a claim by the Virginia Department of Highways and Transportation that more than 400 tractors went past a toll booth without paying. The farmers said they offered to pay, but were waved past the toll booth so traffic wouldn't be held up.

Separately, D.C. Mayor Marion Barry yesterday told city parking officials yesterday to exercise "restraint" in enforcement of the city's parking codes against the farmers.