Jesse L. Jackson announced yesterday that he will seek election this fall as a shadow senator to lobby for D.C. statehood, and said he would seek some of the privileges afforded U.S. senators, including access to the Senate floor.

Although a supporter described the political move as "a great risk," Jackson said his campaign to become a statehood lobbyist will not be a factor in deciding whether to make a third run for the Democratic presidential nomination. He refused to rule out the possibility he would vacate the lobbying post in 1992 to run for president.

"There is no relationship between what we are doing today and the 1992 campaign," he said.

Jackson told more than 100 people gathered at Howard University's Blackburn Center that he intends to expand his role beyond lobbying for statehood, to "put forth a plan to rebuild America."

He was joined on stage by Democratic mayoral candidates John Ray and Walter E. Fauntroy; Bishop George Augustus Stallings Jr. and other ministers; Dorothy Height, president of the National Council of Negro Women; and Mauro Montoya, president of the Gertrude Stein Democratic Club, an influential gay activist group.

Some of those who took part in the gathering lauded Jackson as a potential savior of the floundering statehood movement, citing his stature and ability to generate media attention.

But the statehood effort faces an uphill climb, with or without Jackson. President Bush has indicated he would veto legislation to grant the District statehood, and Republicans on Capitol Hill have said they would block the measure on constitutional grounds and because it would virtually assure the addition of two Democrats to the Senate.

Also, some statehood advocates have expressed concern that their efforts have been damaged by the city's problems with violent crime and finances, as well as by the publicity surrounding Mayor Marion Barry's drug and perjury trial.

Beyond those concerns, Jackson, who faces nominal opposition in the race, would encounter other difficulties in leading the campaign for statehood.

The D.C. Council voted in March to authorize the election of two unofficial senators and a representative to lobby Congress for statehood, but decided against financing the offices and provided only a sketchy description of the lobbyists' responsibilities.

The lobbyists would lack any official standing with Congress and would have to raise money from private sources to pay their own salaries, hire staff and rent office space. They would have no legislative authority beyond recommending action to the council.

In short, they would have far less standing and authority than a council member and essentially would be on par with registered lobbyists.

Some Jackson supporters say those limitations could impede Jackson's effectiveness in dealing with Congress. Others wonder why Jackson, a dynamic political activist, would seek a job that seems beneath him.

"At best, there is great risk in this," said African Methodist Episcopal Bishop H. Hartford Brookins, who attended the announcement. "I am hoping his people will help guide his course."

"I am skeptical that it will add to his luster," said businessman John Hechinger Sr., who said officials with Jackson's National Rainbow Coalition had asked him to run as part of a Jackson slate.

Other Democrats who have filed as candidates for the two shadow senator posts are James Forman, a former civil rights activist; Mark Humphries; Florence H. Pendleton, a longtime Democratic activist; John Moore; Harry Thomas Jr., president of the D.C. Young Democrats; and John West. Seeking the Republican nomination are H. Minton Francis, vice chairman of the Republicans' Capitol Hill Club, and Joan D. Gillison.

Dennis Sobin, who publishes sexually oriented material, is running for a Senate lobbying post.

The Democratic candidates for the representative post are Dearich Hunter, coordinator of the Rainbow Coalition's D.C. statehood campaign, and Charles J. Moreland. Tom Chorlton, who ran unsuccessfully for a D.C. Council seat in 1988, is a Statehood Party candidate.

The Rev. Jerry A. Moore Jr., pastor of 19th Street Baptist Church and a former council member, attended the announcement and predicted that Jackson "will be elected with ease."

Jackson, who shifted his political operation from Chicago to Washington last summer, said D.C. statehood is "the most important civil rights and social justice issue in America today."

He said he intends to travel the country after the campaign, seeking public support for the effort, adding that he may employ civil-rights-era tactics, such as mass protests, to pressure Congress.

Jackson said that, if elected, he will regard himself as a senator and will urge voters to do the same, "so we can get used to being free."

Asked if he intended to seek floor privileges equal to those afforded senators, Jackson said: "We certainly want to have access to them, we want to be a part of hearings . . . . We deserve it."

Jackson said he has held discussions with Senate Majority Leader George J. Mitchell (D-Maine) about how he would be treated in the Senate. "It has not been determined what courtesies the Senate will extend to us," he said.

An aide to Mitchell confirmed that the majority leader has had discussions with Jackson, but could not provide any details of the discussions.