WASHINGTON — In a challenge to Republicans, President Barack Obama urged Congress today to extend expiring tax cuts immediately for all but the highest income earners as a way to eliminate half of the so-called fiscal cliff that threatens to send the economy back into recession.

“What I’m not going to do is to extend Bush tax cuts for the wealthiest 2 percent that we can’t afford and according to economists will have the least positive impact on the economy,” the president said at his first news conference since winning re-election last week.

Standing in the East Room of the White House, Obama pointedly noted he had campaigned on a platform that called for allowing tax breaks to expire as scheduled on Dec. 31 for the wealthiest income earners.

“A modest tax increase on the wealthy is not going to break their backs,” Obama said. “They’ll still be wealthy.”