Sources at CBS News yesterday said that the network plans a prime-time broadcast in mid-September, "probably one hour in length," that will address the issue of enemy troop estimates during the Vietnam war, the main topic of the controversial documentary "The Uncounted Enemy: A Vietnam Deception," which aired on CBS last January.

The broadcast will be "primarily a panel discussion," one source said yesterday, "addressing both sides of the issue."

One CBS News source said yesterday that Vietnam commander Gen. William Westmoreland, the principal target of the original documentary, "has to date not responded in an affirmative way to an invitation to participate in the September program."

The CBS News official said late yesterday that no other invitations have yet been extended to potential panelists.

However, another source said the panel will consist of Sam Adams, the former CIA agent who first brought the story to CBS' attention; retired Col. Gaines Hawkins, who spoke against Westmoreland in the original documentary; George Carver, Adams' superior at the CIA, who is disputing Adams' assertions; and journalists Peter Braestrup, editor of the Wilson Quarterly, and Robert G. Kaiser, an editor at The Washington Post. CBS has told Westmoreland that he could send a representative to participate if he chooses not to himself, the source said. A CBS moderator, probably Diane Sawyer, will anchor the discussion.

CBS sources say the September program will not be specifically a follow-up of the controversy over the original documentary that culminated last month in a critical report issued by CBS News that, while standing by the program, found five violations of CBS News' standards in the broadcast.

The documentary was highly critical of Westmoreland and used the word "conspiracy" regarding his actions during the war, a description the CBS News internal report took pains to emphasize "was inappropriate."

A critical article in TV Guide in late May and pressure from network affiliates prompted CBS News executives to launch an inquiry into the preparation of the Vietnam documentary.

The six-week probe resulted in a 68-page report, buttressed by another 80 pages of footnotes, the highlights of which were released on July 15. The complete text has never been issued. At the time, CBS pledged there would be a future program addressing the issues raised in the original documentary.

Washington public interest attorney Dan Burt, whose Capital Legal Foundation represents Westmoreland, said yesterday that "the general would have to consider the circumstances" regarding any invitation to appear on the September broadcast.

"I would advise the general to do everything he can to clear the air, but whether that is the proper forum I couldn't comment," Burt added.

"I think anyone who goes on that show is going to have to be very cautious about what is said," he said.

Burt asked, "How come CBS is in such a hurry all of a sudden after taking two years to prepare the documentary, and then waiting seven months for another program on the subject, when there are all kinds of documents that participants would have to study before going on the air?"

Burt said he "couldn't comment" on a Variety report that Westmoreland had sought, unsuccessfully, to obtain time on CBS to make an unedited response to the documentary. Westmoreland called the original telecast "a smear."

One CBS News source confirmed yesterday that News president Van Gordon Sauter had received a letter from Westmoreland but said that Sauter did not think "it would be appropriate" to divulge its contents.

However, it has been learned it was apparently a reply to Westmoreland from Sauter that included the invitation to appear on the mid-September broadcast.

Burt would also not confirm the report in Variety that he has threatened to file a $300 million suit against the networkon Westmoreland's behalf.

"Let's put it this way," said Burt. "I haven't written a letter to CBS and I have had no communication from CBS.

"But," he added, "the general has been terribly hurt. He's an honorable man and that program in effect called him a 'traitor.' "

Variety also reported that Sen. Barry Goldwater (R-Ariz.) is so incensed over the CBS documentary that, as chairman of the Senate communications subcommittee, he "has threatened to introduce legislation codifying the financial interest and syndication rules that the networks have been lobbying so hard to get the FCC to lift."

Goldwater's Phoenix office yesterday said the senator was in California and could not be reached.

Regarding the threat of legislative action reported by Variety, Burt said that "the general would not agree in any way to an attempt by anyone in Congress to muzzle the press." Moving Right Along

Although the fact that Navy will have a home game that afternoon could throw a monkey wrench into the arrangements, the NCAA has given a tentative okay that would permit Rockville-based Metrosports to broadcast the football game between those tough Penn State Nittany Lions and the Maryland Terrapins from sold-out Beaver Stadium in University Park, Pa., the afternoon of Sept. 11.

Pending a final decision from the college sports ruling body, Metrosports is talking to local stations as well as a pay-TV channel here about local coverage.

There's also talk that CBS Sports is looking at the Sept. 18 game between the Terrapins and the West Virginia Mountaineers as a possible regional football telecast.

One more Sports Item: ABC Sports yesterday announced that it will begin its coverage of the major-league baseball playoffs (NBC has the World Series this year) on Tuesday, Oct. 5, from the American League West winner's ball park.

The next day, the AL game will be in the afternoon and the National League playoffs will begin that night in the park of the East winner.

If the best-of-five series go five games, the last telecast would be Sunday, Oct. 10.

Trembling Tambourines! After the first five nights of the 12-night summer fund-raising effort at Channel 26, the station has raised $108,508 from 2,898 pledges.

In the wake of the NBC announcement that it's no longer going to underwrite all costs for closed-captioning for the hearing-impaired, the National Captioning Institute announces that it has already received funding to continue the captioning of the network's "Diff'rent Strokes" and "Facts of Life" for the next season (NBC has already agreed to carry previously captioned shows in reruns).

In addition, NCI has received funds to close-caption two Saturday-morning children's cartoon shows, one of which will also be on NBC and the other on ABC, the first time the Saturday schedule has been included in the NCI project.

NCI also announced that Texaco will fund captioning for the "Texaco Star Theatre . . . Opening Night" special on NBC Sept. 11 and Xerox will underwrite an NBC White Paper set for Sept. 21.

Additional funding apparently is near for the captioning of most ABC and NBC prime-time movies in the upcoming season.

In discontinuing its part of the captioning project last week, NBC announced it would pick up the internal costs of future captioning, provided NCI found funds for the initial, more costly captioning process.

The NCI also revealed that the text of President Reagan's Saturday radio talks, which are being renewed this week, will henceforth be included in the teletext service provided the hearing-impaired by ABC every Saturday afternoon.