WASHINGTON — Democrats gave final approval yesterday of a 2009 budget blueprint that rewards domestic agencies and the Pentagon with generous budget increases while leaving wrenching decisions about curbing Medicare costs and increasing taxes to the next president.

The House approved the $3.1 trillion budget plan by a 214-210 vote; the Senate had passed the measure on Wednesday. The nonbinding measure does not go to President Bush but instead sets guidelines for future action by Congress.

The House-Senate compromise relies on questionable assumptions to predict a small budget surplus by 2012 — for the first time since the 2001 budget year.

It would achieve the surplus goal only by allowing many of Bush’s signature tax cuts to expire on schedule in 2½ years and by predicting that the wars in Iraq and Afghanistan will not cost a dime after next year.

The nation’s fiscal condition significantly deteriorated during Mr. Bush’s tenure, and his successor is likely to inherit a budget deficit exceeding $400 billion.

The Democratic plan essentially leaves the budget on autopilot for a year until either Senator McCain, or Senator Obama — the presumptive presidential nominees — can propose a budget.