Washington Redskins owner Jack Kent Cooke indicated yesterday he is moving toward making an announcement concerning a new stadium for his football team, but said he has not reached an agreement with the District government and does have a site outside D.C. available.

"We should be announcing the site and date of construction very shortly," Cooke said. "Now, what very shortly means, I don't know."

He said he is still negotiating with the District government, and "my first choice is the District of Columbia." But he added, "I do have an alternative source."

Mayor Marion Barry's acting deputy press secretary, Cheryl Crowell, said Barry declined to comment on Cooke's statements.

D.C. Armory Board General Counsel Artis Hampshire-Cowan said the Armory Board "remains committed to the Redskins" and is "ready to do this deal."

A source familiar with the negotiations said an agreement that would keep the Redskins in the District had been "conceptually" worked out approximately a month ago.

At that time the source said the new stadium would be built on what is now RFK Stadium's Parking Lot 6 and have a seating capacity of 72,000 to 78,000, including 365 skyboxes. The source said the nearby Langston Golf Course would be "minimally disturbed" by the new facility. Another source said a proposal to fill in a portion of the Anacostia River to provide additional parking spaces had "been dropped for a long time."

Yesterday, however, the source familiar with the negotiations expressed hope that Cooke was satisfied with the arrangement and would endorse a letter of agreement shortly.

In addition, a member of the architectural firm handling the new stadium said the firm has performed initial work on the project and has been working "informally" with the Redskins for the last 1 1/2 to 2 years.

"We've done very preliminary work," said John Selby of Ellerbe Becket's office in Kansas City, Mo. "We're waiting for someone to instruct us to do more."

Cooke said there is no particular time by which his negotiations with the District must be completed, although the Redskins' lease for RFK Stadium will expire after this season.

"That is flexible," Cooke said, "but the sooner it's done, the better."

He said he would like the Redskins to play in the new stadium in fall 1993, and Selby said completion of the new stadium would take "about 28 months from the day construction has authority to proceed."

Authority to proceed will not come until after the project has been approved by a variety of District and federal agencies, including the Congress, which must approve the leasing of public land to a private entity.

The District is seeking to reach a memorandum of understanding with Cooke, but it is unlikely to agree to such a memorandum if it does not believe the project will receive the necessary government approval.