A key member of the bipartisan group of senators searching for months for a solution to the nation's debt crisis says he is "discouraged" and has officially taken a break from the so-called "Gang of Six" negotiations.

"I'm giving it a rest, because we're at an impasse," Sen. Tom Coburn, R-Okla., told Fox. "We have to accomplish certain things if we're going to get a deal, and we're just not where we can meet the demands of what I think we have to have to fix our problems."

Coburn said he had "a frank conversation" with Gang member Dick Durbin of Illinois Tuesday morning, saying, "He agreed that we're at an impasse, and "when you're at an impasse, the worst thing you can do is keep trying to hit your head against the wall until you break your head."

The breakdown, according to sources familiar with the talks, came over disagreements regarding cuts to entitlement programs. The ideological divide is wide and deep between members like Coburn and Durbin on how to reform these programs.

Coburn, known around the Senate has "Dr. No" for his staunch fiscal positions, agreed on the subject of the impasse, saying, "I'm not going to stake fixing our country on something that I don't think will fix it," adding, "Here's the important thing. Medicare will not exist the way it is five years from now. It's an impossibility. We can't borrow enough money for it. Social Security won't exist the way it is 10 years from now. Medicaid absolutely cannot exist, especially knowing we've got 24 million new people coming to it...It can't happen. Nobody's going to loan us that money."

The senator said he thought everyone had been negotiating in good faith, but "right now, I don't think Senator Durbin can give what I need, and I can't give what he needs."

"It's not a matter of bad faith, it's about being a realist about what you can accomplish and what we can't," Coburn said, noting that the group has "got a lot of things agreed to, a lot of pain for both parties, but it's got to be something that I think will actually make some significant differences, and we're just not there to what I think I can sell."

The Gang met earlier Tuesday, sans Coburn, and a key source with knowledge of the gang negotiations, said despite the major hole left by the senator's absence, the group intends to keep on meeting to forge a compromise.

Still, the signal from Coburn is not a good one for any possible compromise. And it will, no doubt, be a discouraging sign to the many senators on both sides of the aisle who are anxiously awaiting a path forward to reduce the debt while also approving a hike in the nation's borrowing limit by the first of August.

Coburn held out hope that he might return to the group at some point, saying, "I'm still a member, I'm just not attending right now."

The senator has been taking heat from some Republicans, like anti-tax advocate Grover Norquist, for supporting what many in his party would call tax increases, as part of the ultimate compromise. But Coburn said that criticism played no role in his decision to leave the gang for now. "Grover Norquist is a fly on the wall. That doesn't matter. What matters is whether we fix our country...I don't care what the criticism is."