The Justice Department asked federal courts in Mississippi yesterday to reject election districts in two counties because they are racially discriminatory.

Any action by the courts could postpone the scheduled Aug. 2 primary elections for the boards of supervisors in Bolivar and Adams counties but would not affect the statewide primary on the same day.

William Bradford Reynolds, assistant attorney general in charge of the Civil Rights Division, asked the courts to allow the department to intervene as a friend of the court in existing cases against the counties.

Under the 1965 Voting Rights Act, Mississippi counties must clear with the Justice Department any changes in election laws or districts. After the 1980 census, all 72 counties were subject to redistricting. Most filed new plans.

The Justice Department has raised specific objections to changes in 14 of the counties, including Adams and Bolivar. Department sources said yesterday that the Civil Rights Division is still debating whether the government should file suits to block primary elections in the other 12.

In the Bolivar and Adams county cases, the courts could either order their own redistricting plan or allow county officials to devise an acceptable plan. Because the primary is less than three weeks away, either action could postpone the local elections.

Frank Parker of the Lawyers Committee for Civil Rights Under Law, which filed the lawsuit against Adams County, has submitted a plan to the court, but the Justice Department has asked the court to let county officials come up with an acceptable plan.

Parker pointed out that 20 other Mississippi counties have not filed redistricting plans for Justice Department approval. He said any local elections in those counties could be technically illegal and open to challenge.

"There are in Mississippi today massive constitutional violations throughout the state involving more than one-third of the counties. We're asking the Justice Department to address this," Parker said.

A department spokesman said the 20 counties have claimed they did not change election boundaries and therefore had no need to file redistricting plans for approval.