Television's always-heated morning wars grew a degree or two warmer yesterday when NBC announced that its "Today" show, oldest of the three early programs, has beaten ABC's long-dominant "Good Morning America" in the national Nielsen ratings for five weeks in a row. It is the first five-week winning streak for the show since March of 1981.

"As I've always said, five weeks is a trend," crowed a moderately ebullient Steve Friedman, executive producer of "Today," but he was joking. Bill McAndrew, network spokesman for the program, was more temperate when he said, "Champagne corks are not popping around here. We're a little too cautious for that." Still, network sources were venturing to suggest that "Today" may have turned another corner in its hard-fought battle to unseat "Good Morning America" from the first-place throne.

"It clearly, clearly is a trend," said NBC News Executive Vice President Timothy Russert from New Orleans, where he had presented the ratings news to a "cheering" regional affiliates meeting. "It's a trend, but it is one that is frankly modeled after the Grant Tinker-Brandon Tartikoff prime-time success. It proves that if you produce a quality program, the audience finds you."

Tinker is NBC chairman and Tartikoff NBC Entertainment president.

For the week ending Jan. 10, "Today" averaged a 5.6 rating and 25 percent share of the viewing audience, compared with a 4.8/21 for ABC's "GMA" and a 3.1/14 for the always-trailing "CBS Morning News." The weekly rating was the highest for "Today" since January 1982 and marked its sixth win out of the last seven weeks.

"There's no question we are neck-and-neck," conceded Phyllis McGrady, "GMA" executive producer. "We are very, very neck-and-neck and have been since early November." But she also said last week was "a little atypical" in that both "Today" and "GMA" scored unusually high numbers in their second hours on certain days.

NBC spokesmen were ready with figures comparing last week with ratings from the same week one year ago. According to these Nielsen numbers, "Today" show ratings are up 14 percent over the same week in 1985 while "GMA" is down 6 percent and the "CBS Morning News" down 8 percent.

"The untold story about morning television is that the audience continues to grow," said Russert. "You don't have to take away viewers from another show for your ratings to go up. Young people who were not weaned on radio now find it very comfortable to wake up and turn on the tube. And Steve Friedman has come up with the perfect mix for them to watch." He praised the program's cohosts, Bryant Gumbel and Jane Pauley.

Whether or not the five-week figures represent a trend, McGrady confirmed that "GMA" staff meetings are being held to combat the "Today" offense. "Yes, of course there are meetings," she said. "When someone is breathing down your neck, as they have been for a year, then you have meetings." McGrady also said that ABC's poor ratings in prime time this season have hurt her show, a point with which NBC sources agree.

But she denied that David Hartman, the "GMA" host and reputed king of morning television, was noticeably upset about the ratings dip, as the boys at "Today" suggested he was. "David is not upset," McGrady said. "He's happy we've made morning television something people talk about and write columns about. Is he happy 'Today' is winning? No. But he is not crazed. No, not at all."

"Today" made several attention-getting splashes last year with trips to Rome, Geneva and Moscow. From Feb. 10-14, the program will originate from Rio de Janeiro and Buenos Aires. But "GMA" has special events planned as well. Most of next Wednesday's program will be devoted to a global round-table discussion among what McGrady calls "real people" in Sweden, Japan, England, the United States, and the Soviet Union or Cuba "or some other Communist country," all discussing current topics like terrorism, health care and the restructuring of the family unit.

Asked to respond to a previous Friedman boast that "Today" tied "GMA" in the ratings last year and will beat "GMA" this year, McGrady said, "Well, that's his motivation. My motivation is to beat him. So, you see, we both have a reason to live."