Virginia and Justice Department officials reached tentative agreement yesterday on a plan to redistrict the state's House of Delegates in a way designed to avoid discriminating against black voters.

The plan must still be voted on by the full Virginia General Assembly -- perhaps as early as next week -- and return to Justice for approval. But it apparently clears the way for fall House elections that had been jeopardized by the Justice veto of the original redistricting plan two weeks ago.

The new House plan represents a compromise between state officials and the Justice Department, which objected to the original one because it diluted black voting strength in two current House districts.

Virginia officials agreed to redraw boundaries to allow the predominantly black city of Petersburg to remain in a black majority district. Justice officials agreed to allow the state to break up a district comprised of four of Virginia's five black majority countries. Each of those counties, along with Brunswick, the state's other black majority county, would be combined with predominantly white counties to form five with majority voting districts.

"The department feels it is comprising to a certain extent," said Justice spokesman Tom Stewart, "but it is a fairer plan than the [Virginia] House had proposed."

Under the district plan in effect over the past decade, three of the state's 52 House districts had black majorities. The compromise plan, if approved, will leave the state with just two -- Petersburg and Richmond. And the Richmond district will lose one of its five seats.

Because the Virginia constitution requires the election of statewide officials "at the time and place of choosing members of the General Assembly," there was some concern that a delay in the House elections would force postponement of elections for governor, lieutenant governor and attorney general.

Another worry for Virginia officials was a hearing before a three-judge federal court in Richmond scheduled for Aug. 13 on eight lawsuits filed against the original House plan. Without Justice approval, the court would technically not have any plan to consider.

The Justice Department's involvement in the Virginia redistricting plan devised by the legilature following the 1980 census was mandated under the 1965 Voting Rights Act. Virginia is one of 22 states required under that law to submit all changes in election districts for Justice review to ensure fair treatment of minorities.

Yesterday's agreement between the Justice Department and Virginia officials came after three days of closed conferences in Washington that were criticized by some state black leaders.

"Can these people go up there and negotiate a changed plan without any other input?" asked Gerald Poindexter, the county attorney for Surry, one of five predominantly black counties that Justice ruled had suffered racial discrimination under the original plan. "Are there any black people there?" he asked. There were no blacks in the delegation that met with Justice officials.

The Rev. Curtis Harris, who heads the Virginia chapter of the Southern Christian Leadership Conference, had scheduled a meeting with Justice officials for this morning, before learning that a deal had been made. Harris said reports that boundary lines were being "jiggled and juggled" in private sessions made him anxious.

"We want to jiggle and juggle a little with Justice ourselves." said Harris.

Justice spokesman Stewart said yesterday that when Virginia officials return to Washington with approval of a plan, it will be given "instant attention."

The Justice Department has also rejected the Virginia Senate's redistricting plan, on grounds it would discriminate against black voters, particularly in the Norfolk area. Negotiations with Justice on that plan have been postponed, since Senate elections won't be held until 1983.