U.S. President Barack Obama talks about fiscal cliff negotiations as he takes questions from reporters at the White House on Wednesday. (Charles Dharapak/Associated Press)

Optimistic despite a tightening deadline, U.S. President Barack Obama said Wednesday he and House Speaker John Boehner are "pretty close" to a grand fiscal deal to avoid a first-of-the-year shock to the economy, but that congressional Republicans "keep on finding ways to say no as opposed to finding ways to say yes."

Obama cast a resolution to the "fiscal cliff" as a matter of political will. He said in the aftermath of the massacre of school children in Connecticut, the nation deserves a compromise by its political leaders.

"If this past week has done anything, it should just give us some perspective," he said. And he urged lawmakers to "peel off the partisan war paint" and strike a deal.

Obama's comments came shortly after the White House threatened to veto Boehner's backup plan for averting the "fiscal cliff."

Boehner's measure, a so-called Plan B, would block tax increases from being triggered Jan. 1 on everyone but those whose incomes exceed $1 million.

Boehner is planning a House vote on his proposal on Thursday, hoping it would raise pressure on Obama to make concessions as both sides continue reaching for a bipartisan deal on averting the "fiscal cliff."

Without an agreement among lawmakers, broad tax increases on nearly all taxpayers and budget-wide spending cuts will be triggered in early January.

Boehner defiant

Boehner responded to Obama with a defiant tone. In an appearance before reporters that lasted under a minute, Boehner called on Obama to offer a deficit-cutting plan balanced between spending cuts and tax increases and predicted that the House would pass his backup plan.

"Then the president will have a decision to make," Boehner said. "He can call on the Senate Democrats to pass that bill or he can be responsible for the largest tax increase in American history."

Obama dismissed Boehner's proposal, saying it would not provide unemployment insurance for 2 million jobless Americans and would result in higher taxes for families that benefit from various tax credits.

"That violates the core principles that were debated during the course of this election and that the American people determined was the wrong way to go," Obama said. Instead, Obama said, he and Boehner in their own talks had moved significantly toward each other before talks reached a lull on Tuesday.

"What separates us is probably a few hundred billion dollars," Obama said. "The idea that we would put our economy at risk because you can't bridge that gap doesn't make a lot of sense."