More than $500 billion in tax hikes and across-the-board spending cuts are set by law to take effect at year's end without a deal.
Obama also vowed he would not let Republicans use raising the U.S. debt limit as pressure to reach a deal on their terms. Asked whether he would negotiate on the debt limit, the president said, "No. And I've been very clear about this."
"Frankly up until about a couple of days ago, if you looked at it, the Republicans in the House and [U.S. House] Speaker [John] Boehner I think were in a position to say: 'We've gotten a fair deal,'" Obama said. "The fact that they haven't taken it yet is puzzling, and I think, you know, a question that you're going to have to address to them.
"I remain optimistic, because if you look at what the speaker has proposed, he's conceded that income tax rates should go up, except right now he only wants to have them go up for millionaires," he added. "If you're making $900,000, somehow he thinks that you can't afford to pay a little more in taxes. But the principle that rates are going to need to go up, he's conceded.
"I've said I'm willing to make some cuts. What separates us is probably a few hundred billion dollars. The idea that we would put our economy at risk because you can't bridge that gap doesn't make a lot of sense."
Obama offered a plan Monday that would raise tax rates on income above $400,000 -- a change from his earlier insistence on the increase affecting income over $250,000. Obama's offer would produce $1.2 trillion in tax increases and cut $930 billion in spending over 10 years.
Asked what happens next, the president said, "I'm going to reach out to all the leaders involved over the next couple of days ... and find out what is it that's holding this thing up. What is holding it up? If ... the argument from Republicans is we haven't done enough spending cuts, that argument is not going to fly because we've got close to a trillion dollars of spending cuts."