Negotiations between Washington Redskins owner Jack Kent Cooke and the D.C. Armory Board about a new football stadium that would keep the Redskins in the District have reached at least two points of contention that could threaten Mayor Marion Barry's ability to conclude an agreement before his term expires Jan. 2, a source familiar with the negotiations said yesterday.

Cooke, whose team's lease for RFK Stadium expires at the end of this season, has said he is willing to build a facility with his own money that sources have said would accommodate 72,000 to 78,000 seats and be constructed on what is now RFK Stadium's Parking Lot 6. But Cooke again has raised the issue of filling in a portion of nearby Kingman Lake, an offshoot of the Anacostia River, in order to accommodate new parking spaces and is requesting year-round control of all parking lots that currently serve RFK Stadium and the Armory and also would serve the new stadium, the source said.

"In his last meeting with the mayor, he told him {Barry} these are two things he had to have," said the source, who characterized each of Cooke's requests as a potential "deal-breaker."

Cooke wants "the locks to the gates" of the parking lots, the source said -- a situation that would be tantamount to giving Cooke the ability to determine what events could be held at RFK Stadium and the Armory. "Any promoter would have to talk to him first," the source said.

The environmentally sensitive issue of filling in a portion of Kingman Lake was believed to have been settled, with both sides agreeing the lake would not be disturbed. This is an important element of the negotiations because federal land is involved. As a result, the National Park Service and the Interior Department will have to approve any proposal for a new stadium.

Interior Secretary Manuel Lujan Jr. "would be disinclined to approve a plan that involves filling in the lake," Interior Department spokesman Steve Goldstein said. "Manuel Lujan is a football fan like everyone else, but that doesn't supersede his responsibility as secretary. There are certain environmental regulations that have to be carried out. We usually are not in the habit of filling in lakes so that individuals will have to walk a little bit less to attend a football game."

Goldstein also said his department "is not anticipating any movement" on the project until after the mayoral election Nov. 6.

Cooke reiterated his position of not commenting on the negotiations.

"I intend not to negotiate any deal with the city or anybody else by way of the media," he said.

Barry, who chairs the Armory Board, also declined to comment on the specifics of the negotiations.

Asked about his ability to conclude an agreement before leaving office, Barry replied: "I'm going to try as hard as I can. If I don't, I won't. I've given it three years of my time already and we're going to continue until the last moment to try, but I don't want to discuss what brings us together or what separates us. The only thing I know is that Mr. Cooke and I agree that the Redskins ought to stay in Washington. We will continue to try to negotiate that out. . . . It's not at the top of my agenda, but I'm going to work hard on it."