WASHINGTON — With “fiscal cliff” talks at a partisan standoff, President Obama and House Speaker John Boehner swapped barbed political charges 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 added 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.

Boehner expressed confidence the Republicans’ narrow, so-called Plan B bill would pass the House on Thursday despite opposition from some conservative, anti-tax dissidents. 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.