Even late-night TV gets the blues, as two of TV's most trusted personalities worked through what was perhaps their most difficult night.

David Letterman returned to the airwaves Monday in a low-key Late Night, which saw veteran CBS news anchor Dan Rather break into tears.

The normally stoic newsman twice got choked up when talking about last Tuesday's devastating terrorist attacks on the World Trade Center and the Pentagon, which killed thousands of people.

Rather first broke down after speaking about the brave rescue efforts by firefighters responding to the World Trade Center disaster. He then became teary-eyed again while attempting to recite a line from "America the Beautiful."

"Who can sing now with the same meaning we had before...one stanza that goes, 'Oh beautiful with patriot's dream that sees beyond the years / Where alabaster cities gleam / Undimmed by human tears,'" said Rather, reflecting on the destruction of the twin towers.

Rather paused to regain his composure and apologized for breaking down as he was comforted by an emotional Letterman.

"You're a professional, but, good Christ, you're a human being," said Letterman, putting his hand on Rather's arm.

Rather--who appeared on Letterman's first broadcast since last Tuesday's tragedies and has covered everything from President Kennedy's assassination to the Challenger disaster--logged more than 15 hours a day anchoring CBS' news coverage of the "Attack on America." He was joined on Late Night by Letterman's good friend and Who Wants to Be a Millionaire host Regis Philbin, who provided the evening's lighter moments.

When asked whether his former cohost Kathie Lee Gifford would come back, Regis replied, "[Now] there is somebody who can end this in a hurry! You want a quick end to this? Send Kathie Lee over there!"

The remark drew some welcome laughs from the audience. Reege and Dave also agreed to finally make good on their dinner date, which has been a running joke between the two for years.

But Letterman's interview with his pal wasn't without its serious side: Philbin's son was working in the Pentagon when it was hit by the hijacked airplane, but he was on the other side and out of harm's way.

Answering New York City Mayor Rudy Giuliani's call to return to work in the wake of the tragedies, Letterman eschewed the usual wisecracks and daily Top 10 List in favor of a more moving and somber show, which reflected the dampened mood of the nation.

The gap-toothed comic also gave an unscripted nine-minute monologue expressing his feelings about the tragedies.

"It's terribly sad here in New York City...you can feel it, you can see it," said Letterman, his voice at times shaky and subdued. "Mayor Giuliani encouraged us and...implored us to go back to our lives, go on living, continue trying to make New York the place that it should be. And because of him, I'm here tonight."

Letterman also praised the brave men and women of New York City's fire and police departments whose lives were lost in the subsequent rescue effort.

The tone Letterman set Monday night will likely be followed by other talk shows as they grapple with the horrors of last week's events. Bill Maher expressed outrage at the acts as Politically Incorrect resumed Monday. Craig Kilborn also returned to his show Monday night, while Conan O'Brien and Jay Leno plan to return to the air Tuesday night.

One source told Reuters that the Tonight Show host and his army of writers have been "struggling" to write a monologue that would strike the right note between "what's appropriate and what's not."

Meanwhile, on Tuesday morning, Live with Regis and Kelly had Philbin interviewing rescue workers on the scene at "ground zero," while partner Kelly Ripa showed off her patriotism by wearing a red, white and blue dress.

And in a moving tribute to her hometown, Rosie O'Donnell opened her show with a sad musical montage of New York City and its rescue efforts, using footage shot by Rosie herself.

"I, like many New Yorkers, was terrified to come back," the talk-show host said, before quoting a line from Les Miserables: "There's a grief that can't be spoken, and the pain goes on and on."

O'Donnell then expressed her thanks to Mayor Giuliani, whom she praised for helping the city get back on its feet, before showing a home video of her children.