(Alex Brandon/AP)

Sens. Saxby Chambliss (R-Ga.) and Mark Warner (D-Va.) told reporters that they were hopeful Coburn would one day return to the group and acknowledged that his absence has made their work more challenging. Warner emphasized, however, that he believes the Senate working group, rather than a separate group being led by Vice President Joe Biden, offers the best possibility for a broad deficit-reduction deal.

“I still think the best hope and the best chance is a bipartisan effort that starts in the Senate,” Warner said. “We’ve got a few things to resolve, and clearly Tom Coburn added a lot of value to this group. ... But I don’t think that we can say that we should stop simply because one member of the Senate” dropped out.

Chambliss, one of the two Republicans remaining in the group, said that he and Coburn planned to have dinner together Wednesday evening. “Oh, I ask him back at least once a day,” he said, laughing.

“Certainly it’s been more difficult because Tom was a very valuable member; he has great ideas and really knows the issues well, particularly having served on the deficit commission,” Chambliss added. “So it’s important that at the end of the day we have a strong bipartisan group, and I hope that Tom Coburn is a member of that when we conclude and make a presentation.”

Chambliss and Warner made their remarks to reporters after addressing a luncheon crowd at an event hosted by the Economic Club of Washington. Among the more than 200 people attending the event were the ambassadors from India and Switzerland.

Aside from Chambliss and Warner, the other three lawmakers currently involved in the bipartisan working group are Sens. Dick Durbin (D-Ill.), Mike Crapo (R-Idaho) and Kent Conrad (D-N.D.).

The two senators spoke one day before another bipartisan working group headed by Vice President Biden is slated to hold its fifth deficit-reduction meeting at the Capitol. Republicans are seeking a deal that includes as much as $2.5 trillion in budget savings in exchange for a vote to raise the debt ceiling through the end of next year.

Warner said Wednesday that he doesn’t believe there’s conflict between the two groups, although he said that he was worried that the Biden-led group may end up arriving at a compromise that falls short of the goals of the “Gang of Six.”

“One of my concerns about the debt ceiling negotiations is that if we kind of limp through the lowest-common-denominator debt ceiling extension -- what’s the minimal amount to cut to get through a short-term extension -- we may have the time, the bond markets may respond okay, but I don’t know how big this window is [for greater reform],” Warner said.

He later added that “the problem with a short-term extension is, if you don’t have a long-term plan, you bump up against this again, and at what point do the markets run out of patience that we’re going to put a long-term plan together?”

A long-term deficit reduction plan, Warner argued, “would be the single greatest jobs stimulus that we could do right now.”

Chambliss said that he was “optimistic” about the progress the Biden-led group was making but wouldn’t “hazard a guess right now” on whether they’ll be able to hash out a deal before Aug. 2.

“It’s a very different atmosphere in Washington from any time in the 17 years I’ve been here,” Chambliss said.

As some members of Congress have dismissed the notion that failing to raise the debt ceiling would automatically equate to default, Warner on Wednesday argued that such statements show irresponsibility and “a remarkable lack of Economics 101.”

“It would be inexcusable,” Warner said of failing to raise the debt ceiling. “We all ought to be fired if this is allowed to happen.”

Even as Warner and Chambliss emphasized that the “Gang of Six” has continued to meet, the two senators declined to give any timeline for a final plan, noting that their discussions are not linked to the ongoing debate over raising the country’s $14.3 trillion debt limit.

“We’re not focused on the debt ceiling vote,” Chambliss said. “We were not focused on the [continuing resolution] vote. We’re focused on getting a proposal that is right and moves us in the right direction, whenever that may come.”