Key D.C. civic leaders said yesterday that plans for a $80 million to $100 million civic center in downtown Washington appeared closer to reality than ever before following reports that Rep. William R. Natcher (D.Ky.) had dropped his previous opposition to such a project.

However, announcement of Natcher's new interest in the project also set the stage for a possible fight over which Washington area jurisdiction would get federal funds to build a center. (SECTION) oon after news of Natcher's change of mind became known yesterday, Prince George's County Executive Winfield M. Kelly Jr. sent Natcher a reminder that Kelly's government also would like to build a civic center and felt that it could do the job at less cost to the federal government.

Natcher, chairman of the House District Appropriations subcommittee, was considered to be among influential congressmen whose opposition played an important part in Congress's scuttling plans for a proposed Eisenhower Civic Center in 1974.

Del. Walter E. Fauntroy (D-D.C.) said yesterday that Natcher has since been impressed with support for the project by the Metropolitan Washington Board of Trade, which believes the center could be an economic boon to the city.

Fauntroy said Natcher now appears willing to support a downtown civic center in the District if the city agrees to repay a $600,000 bank loan taken out to plan the ill-fated Eisenhower project and adopt the civic center plan as part of its annual public works package.

As part of the city's regular building program, money for the project would have to be approved by Natcher's subcommittee.

Appropriations for the proposed Eisenhower center would have been routed through a different congressional committee.

D.C. Mayor Walter E. Washington, city planners and several members of the City Council said yesterday that Natcher's support, even though linked to the two conditions, was a definite boost to civic center efforts.

"We're a hulluva lot closer with his (Natcher's) OK than we were when we had to convince him of its merits," said Ben W. Gilbert, director of the Municipal Planning Office. "I think it's very real at this point."

"He's ready to go forward, the mayor is ready to go and we're ready to go," said Council member Marion Barry (D-at large). "Prince George's keeps rattling around, but this gives us the competitive edge. Everybody recognizes that the center ought to be in Washington."

Several key Council members felt that both conditions set by Natcher would not be hard to meet. One ranking city official said a plan could be approved as early as this fall.

One major obstacle still faced by the city is the choice of a site for the center, which is expected to occupy an area of about 300,000 square feet, or about two city blocks.

The most talked about site now, Gilbert said, is near Mount Vernon square in Northeast Washington, an area bounded by 8th and 10th Streets on the east and west and New York Avenue and H Street on the north and south.

This was the favored site for the Eisenhower Center, but it became controversial because of the necessity to relocate many businesses. Opposition also focused on the projected relocation of many Chinese-Americans, who now live, work and shop in the area.

Another problem, city leaders said, will be the financial feasibility of the project. If the center does not bring in enough revenue annually to pay principal and interest on loans taken out to finance it, an increase in city property taxes or cuts in city services would follow.

Barry, chairman of the Council's finance and revenue committee, said some type of special tax for businesses directly benefitting from the project might be used as a way to offset loan repayment costs. An 80-cent to $1 (per room, per day) hotel tax is one option that has been discussed, he said. Barry said the civic center itself could bring the city as much as $6 million to $8 million each year.

Council member Nadine P. Winter (D-Ward 6) said she believes some community groups that previously opposed the project have done an "about face."

"They're now supporting business downtown because they think it may spill over onto the H Street Corridor. They also realize we have to do something other than give out welfare checks - we have to create jobs."

District officials had been expected for sometime to announce a new offensive to gain support for the center. Those plans were stalled because of the current controversy in city government over alleged mismanagement and financing of Mayor Walter E. Washington's 1974 election campaign.

Knowledgeable sources at the District Building said some businessmen were urging Mayor Washington to launch the effort as soon as possible. Others advised a delay in the civic center push because some of the land in the Mount Vernon Square area is owned by Leonard B. Doggett Jr., a principal fund raiser for the mayor's 1974 campaign.

The mayor was told that in the context of controversy about that campaign, an all-out push for the civic center might be viewed - incorrectly - as a favor to Doggett, the sources said.

Kelly of Prince George's in a telegram to Natcher yesterday, "heartily endorsed the involvement of the federal government in the funding of a regional convention center."

Kelly said such a center in Prince George's could be built for $50 million. Only $25 million of that amount would have to be provided by the federal government, Kelly said, "because we believe the state will provide 125 million in matching funds."