LOS ANGELES, JULY 17 -- NBC today announced a major restructuring of the management of its entertainment division, promoting longtime president Brandon Tartikoff, 41, to the new position of chairman of the NBC Entertainment Group.

Tartikoff's top three deputies -- who have been with him for the past 10 storybook years at the network -- were all moved up a notch in the restructuring.

NBC President Robert Wright, who announced the changes today at the semiannual network press tour, said he and Tartikoff had been discussing some such changes for nearly two years.

Wright said the announcement "speaks for itself: We're uniquely capable of promoting our own people." He called Tartikoff "a brilliant competitor, an innovative strategist and our not-so-secret weapon."

The NBC Entertainment team just completed a fifth straight year as the prime-time leader of the networks. At one point in its streak, NBC, under Tartikoff, won 68 straight weeks, until ABC took over during the World Series week last October, and then promptly launched another unbroken string at the top.

But the competition has been tougher the past two years. Upstart Fox Broadcasting and a reviving ABC have helped narrow the spread between first and last in the weekly prime-time ratings race.

This May Tartikoff announced nine new series for the fall 1990 season. First reports indicate that it's a strong replacement schedule. "We believe our development {for 1990-91} is the best in years," Wright told reporters today.

So the timing for a Tartikoff team move was as good as it was going to get for the predictable future.

Tartikoff is expected to spend more time with NBC Productions, which he already heads, and as chairman of the Program Development Group formed 18 months ago, in which he coordinates long-range planning with the presidents of news, sports and owned-TV station divisions at the network. But Tartikoff will still have a strong voice in the operations of the entertainment division. As for a precise reassignment of duties, Wright said today the four executives will "work that out themselves."

Warren Littlefield, who has been executive vice president for prime-time programs, succeeds Tartikoff as president of the division.

Perry Simon, who has been senior vice president, series programs, will replace Littlefield.

John Agoglia, who has been executive vice president of NBC Productions, was named to the newly created job of president, NBC Enterprises, and will continue to oversee business affairs activities and have management responsibility for NBC's videocassette joint venture with Columbia.

Littlefield, whom Tartikoff said had, in effect, been running the division for the past 18 months anyway, will continue to consult with his boss over the key scheduling and programming decisions.

Littlefield, who has been more and more visible in recent months as a spokesman for NBC Entertainment, said, "I'd never be so foolish as to say I'd ignore Brandon... . Over the last couple of years, we've worked on the schedules and we've been able to say, {in concert} 'This is the schedule I want to see on the air.' "

Tartikoff said he envisioned "the arrangement working like I was allowed" when then-NBC chairman Grant Tinker was in charge. "I could run around giving out {deals for} pilots" but was still checking regularly with the boss.

"They don't need me to be over their shoulders," said Tartikoff.

While he will not be "disappearing" from those day-to-day operations, Tartikoff said he began over at least the past 18 months to understand the need for taking the longer view.

He recalled sitting in negotiating sessions for series producers and their stars with his top three deputies and feeling "such a sense of overkill in the room" while "a parade of missed opportunities was going by" outside, with the 1990s just around the corner.

He said the Program Development Group would command a lot of his time. He'd like to focus on "the big picture" in the late-night area -- an acknowledgment that the Johnny Carson era will be drawing to an end in a couple of years -- and also in the early-morning area.

Tartikoff will also focus on NBC Productions, which has had a mixed record over the years in the miniseries and movie areas but has recently been credited with the award-winning "Roe vs. Wade" and "An Early Frost" movies (the latter being the first movie to dramatize the devastating effects of AIDS) and, as far back as 1986, the "Peter the Great" miniseries.

Although there have been rumors off and on for years that the premiere TV programmer in the business was getting tired of the grind, today's announcement seemed to say Tartikoff was still very much in the game for NBC.

"I hope Brandon is going to be with us a long time," Wright said.