WASHINGTON — “Fiscal cliff” talks at a partisan standoff, President Barack Obama and House Speaker John Boehner swapped barbed political charges on Wednesday yet carefully left room for further negotiations on an elusive deal to head off year-end tax increases and spending cuts that threaten the national economy.

Republicans should “peel off the war paint” and take the deal he’s offering, Obama said sharply at the White House.

He buttressed his case by noting he had won re-election with a call for higher taxes on the wealthy, then he said pointedly that the nation aches for conciliation, not a contest of ideologies, after last week’s mass murder at a Connecticut elementary school.

But he drew a quick retort from Boehner when the White House threatened to veto a fallback bill drafted by House Republicans that would prevent tax increases for all but million-dollar earners. The president will bear responsibility for “the largest tax increase in history” if he makes good on that threat, the Ohio Republican declared.

In fact, it’s unlikely the legislation will get that far as divided government careens into the final few days of a struggle that affects the pocketbooks of millions and blends lasting policy differences with deep political mistrust.

Boehner expressed confidence the Republicans’ narrow so-called Plan B bill would clear the House today despite opposition from some conservative, anti-tax dissidents, but a cold reception awaits in the Democratic-controlled Senate.

The leadership worked to shore up the measure’s chances late in the day by setting a vote on a companion bill to replace across-the-board cuts in the Pentagon and some domestic programs with targeted reductions elsewhere in the budget, an attempt to satisfy defense-minded lawmakers.

As for a broader agreement, officials said there had been little if any progress toward closing the gap between the two sides in the last two days, even though aides to the president and Boehner have remained in contact.

On paper, the two sides are relatively close to an agreement on major issues, each having offered concessions in an intensive round of talks that began late last week.

But political considerations are substantial, particularly for Republicans.

After two decades of resolutely opposing any tax increases, Boehner is seeking votes from fellow Republicans for legislation that tacitly lets rates rise on million-dollar income tax filers. Despite vehement protests that the looming across-the-board spending cuts would seriously affect the Pentagon, the leadership’s fallback bill does nothing to blunt or eliminate the reductions scheduled to begin Jan. 1.

Boehner won a letter of support from anti-tax activist Grover Norquist during the day. Norquist’s organization, Americans For Tax Reform, issued a statement saying it will not consider a vote for the bill a violation of a no-tax-increase pledge that many Republicans have signed.