ABC News named Elizabeth Vargas and Bob Woodruff as its evening news co-anchors yesterday, opting for a younger and more diverse look for the coveted assignment after failing to reach an agreement with veteran Charlie Gibson.

Four months after the death of Peter Jennings, ABC is gambling on the first dual-anchor and male-female pairing on a network evening newscast since the ill-fated coupling of CBS's Dan Rather and Connie Chung more than a decade ago. ABC executives were clearly reluctant to break up a successful "Good Morning America" team by tapping Gibson, 62, and "World News Tonight" had already been using Vargas, 43, and Woodruff, 44, as temporary anchors.

Gibson wanted the job, but the two sides could not strike a deal.

Vargas, who was raised by a Puerto Rican father and an Irish American mother, said yesterday that she brings a different mix of views to the job because "I'm a woman, I'm a working mother, I'm a minority. Being a mom is the biggest, most important role in my entire life. . . . Especially as a woman, I really, really want to do this well. It's important to have a woman be successful in this role."

Filling in after Jennings's death "has been tough and trying and tragic for everyone here," she said. "Bob and I are taking seriously the legacy he left behind, to do hard news and do it well. We've been really lucky the audience has stuck with us in this time of uncertainty."

Woodruff, who told the staff "this is awesome," said the arrangement will free him to continue his field reporting. "Peter used to say to me, 'Be careful what you wish for, because you're going to end up in a chair and not out on the stories you love.' " In the past, said the lawyer-turned-journalist, "I wanted to become the best damn foreign correspondent in the business. I never really thought about anchoring."

ABC News President David Westin actually offered the job to Gibson last week, but not on terms he could accept, according to two sources familiar with the process who declined to be identified discussing details of personnel matters. Gibson wanted to remain anchor through the 2008 elections, while Westin was offering only a two-year tenure, with duties to be shared with Vargas and Woodruff in a three-anchor arrangement.

"I'm very pleased for them and hoping they'll have a long and successful run," Gibson said, adding that he is quite happy on the morning show. "David and I had long discussions, which simply broke down over the issue of the length of time to do it."

Westin gave the new anchors the news Thursday, with Woodruff in his New York office after returning from Mississippi and Vargas on the phone from New Orleans, where she had just been dispatched. While neither is as well known as Jennings at the end of his life, Westin said, "both Bob and Elizabeth will be earning that relationship day after day with the quality of what they put on the air."

The new duo will be competing with 46-year-old Brian Williams, whose "NBC Nightly News" leads the ratings pack, and possibly Katie Couric, 48, if CBS's aggressive effort to lure her from "Today" to succeed Bob Schieffer is successful. The ABC newscast has maintained its second-place ranking under Vargas and Woodruff.

The anchors plan to remain on duty for an additional three hours each night to deliver two live versions for the western United States -- sometimes with different lead stories -- a first for the broadcast networks. ABC says that both will contribute to a daily blog and that parts of "World News Tonight" will be made available online even before the broadcast. Williams has pioneered anchor-blogging, and both NBC and CBS have been putting their newscasts on the Internet in different forms.

Despite these new wrinkles, the networks seem to be preserving the basic franchise after two decades of eroding audiences and criticism that 6:30 newscasts are anachronisms in an age of round-the-clock news. The programs still reach a combined audience of 25 million, and although the departure of Dan Rather, Tom Brokaw and Jennings after more than two decades sparked talk of a radical departure, change comes hard.

"The evening news is locked into two things -- a half-hour format and the existing time slot," said Bob Zelnick, a former ABC correspondent who now chairs Boston University's journalism department. "You can talk about ensembles, guys parachuting in from Comedy Central, new formats that appeal to bubblegum-chomping 12-year-olds, but you can't do it."

Steve Friedman, a former executive producer of "Today" and CBS's "Early Show," said the male-female pairing "is what people are used to seeing in local news." Friedman foresees an "indoor-outdoor show" in which Woodruff spends much of his time racing to breaking-news events.

"Anybody who goes in there and tries to reinvent the wheel is going to lose," he said. "You have to put different spokes on the wheel."

Erik Sorenson, a former president of MSNBC, said "there are some real advantages" to being able to dispatch one of the anchors to various hot spots, "but not a lot of benefit with two people sitting within three feet of each other."

Said Sorenson, who was executive producer of the "CBS Evening News" during the failed Rather-Chung experiment of the early 1990s: "The downside is, it's a 22-minute broadcast and you're splitting up the fact time between two people. . . . There's certainly some risk for ABC to do this, but this is the time to take a risk."

During the swirl of speculation about the decision, many industry insiders, including some ABC staffers, expected Gibson to get the nod, even though he and Diane Sawyer have been closing the ratings gap with Couric and Matt Lauer at "Today." As recently as last month, Woodruff explored the possibility of jumping to another network and had a conversation with Sean McManus, the new president of CBS News, who did not make an offer, according to industry sources who declined to be named because of the sensitivity of personnel discussions.

"Charlie has always loved 'World News Tonight' " and would have been "perfectly happy" to take the job, Westin said, praising what he called Gibson's "heroic" double shifts after Jennings's death. Gibson, who initially rotated the evening duties with Vargas, gave way to Woodruff in September after contracting pneumonia.

"Let's be honest, they're younger, they're prettier," Emily Rooney, a former ABC producer, said of Vargas and Woodruff. She said Woodruff has more "gravitas" but that both anchors bring appealing qualities to the job.

"Bob Woodruff is brilliant," said Rooney, who hosts two talk shows on Boston's WGBH-TV. "He can ad-lib and put information out in a seamless manner. Elizabeth, I think, is very serious and studious. She's not the classic prima donna. I don't think anybody will resent her."

Vargas, a "20/20" co-anchor who will continue in that role, is the better-known of the two, having been a substitute anchor for several years, including during the death of Ronald Reagan and the Elian Gonzalez case, which won her an Emmy.

She grew up as an Army brat, in Germany and Okinawa, without a television, and her first job -- while in college -- was Saturday anchor for the ABC affiliate in Columbia, Mo., for $3.35 an hour. After stints in Reno and Phoenix, where her bosses "told me I was a lousy anchor," she joined CBS News in Chicago and later became a correspondent for NBC's "Dateline."

Vargas has handled a range of feature stories not normally associated with an evening news anchor, hosting one-hour "Vanished" specials about missing people, along with programs on same-sex marriage, surrogate parenting and miracles.

Woodruff is better known as a field reporter, having won attention for his coverage of Hurricane Katrina and the Asian tsunami, as well as his reporting from Afghanistan and as an embedded reporter during the U.S. invasion of Iraq.

A New York corporate attorney who moved to China to train lawyers in 1988 -- two days after what he calls a "shotgun wedding" -- Woodruff wound up working as Rather's "fixer" and translator in the aftermath of the Tiananmen Square uprising.

He "caught the journalism bug," abandoning the law to become an NBC local reporter in Redding, Calif., Richmond and Phoenix. Woodruff joined ABC for stints in Chicago, London and Washington, where he covered the Justice Department during the Clinton administration.

Although the new broadcast doesn't launch until Jan. 3, the two will essentially be co-anchoring next week when Vargas heads for Baghdad to cover the Iraqi elections.

Elizabeth Vargas and Bob Woodruff in the "World News Tonight" studio after ABC's announcement. They officially take over as co-anchors of the broadcast on Jan. 3.