WASHINGTON (AP) — Republicans aren't budging on tax rates, and Democrats are resisting steps like raising the eligibility age for Medicare. Negotiations on averting a year-end fiscal train wreck combining big automatic tax hikes and sweeping spending cuts again appear stalled.

There are less than three weeks before the government could careen off this "fiscal cliff," but the chief GOP negotiator, House Speaker John Boehner, R-Ohio, said Wednesday that "serious differences" remain between him and President Barack Obama after an exchange of offers and a pair of conversations this week.

Boehner spoke after a closed-door meeting with fellow GOP lawmakers in which he advised them not to make plans for the week after Christmas.