U.S. Rep. Parren J. Mitchell, a Baltimore Democrat who announced seven months ago that he will not seek another term in the House, is reconsidering his decision to retire, according to supporters who met with him this week.

The 16-year House veteran's apparent wavering follows reports in recent weeks that his nephew, state Sen. Clarence M. Mitchell III, is under investigation by the FBI for possible obstruction of justice and perjury.

Clarence Mitchell, who had been expected to declare his candidacy for his uncle's seat, abruptly canceled a scheduled announcement earlier this week and told supporters he was considering running again for his state Senate seat.

Clarence Mitchell had announced early last month that he planned to resign from the Senate. Parren Mitchell had made it clear that he would support Clarence Mitchell's bid for Congress if he decided to run.

"It is obvious that there is an across-the-board community sense that the majority of people in the 7th District are hoping Parren Mitchell will change his mind," Clarence Mitchell said. "I would run for the Senate again. Certainly I wouldn't be running against Parren."

Clarence Mitchell said his final decision would not be affected by an ongoing federal investigation into his ties to convicted Baltimore heroin kingpin Melvin D. (Little Melvin) Williams. The Washington Post reported last month that federal authorities are investigating whether Mitchell arranged fabrication of financial documents to support allegedly false testimony he gave to a federal grand jury last May.

Parren Mitchell met Thursday evening with a group of black ministers, who urged him to run for reelection. After the meeting at New Psalmist Baptist Church, he told The Baltimore Sun: "We just had a good long talk, and we're going to meet again."

The Rev. Walter Thomas, who is the New Psalmist pastor and the president of the city's Baptist Ministers' Conference, said he was encouraged by Parren Mitchell's responses at their meeting.

He said the ministers, who have urged Parren Mitchell for some time to stay in Congress, made an appeal to him again this week because they believe an incumbent will be a more effective voice for the largely black 7th District during the last two years of the Reagan administration.

"We felt we didn't need some freshman in Washington trying to learn the ropes while stuff is dying up in Annapolis," he said. "This is a time when we need a seasoned man fighting for us."

Other announced candidates for the congressional seat include Del. Wendell H. Phillips, Morgan State University Professor Augustus Adair and Baltimore City Council member Kweisi Mfume. All are Democrats.