The Senate approved a Democratic budget plan Friday that promises a balanced budget in five years by mixing spending increases with renewal of expiring tax cuts.

The $2.9 trillion budget outline won approval on a 52-47 vote, but only after Democratic moderates rewrote it to favor extending popular tax cuts that are to expire at the end of the decade.

The most immediate impact would be to sanction big spending increases when lawmakers later this year write budget bills for the Pentagon and domestic Cabinet agencies.

The vote was a victory for Senate leaders who viewed passing a budget as a key sign of Democrats' ability to govern. Two Republicans joined them, Sens. Olympia Snowe and Susan Collins of Maine.

Congress failed to pass a budget last year, and Democrats didn't even bring one to the floor when controlling the Senate in 2002.

The Democratic blueprint is nonbinding but sets guidelines for follow-up legislation.

It also would require that lawmakers seeking to cut taxes or boost benefit programs — such as Medicare, children's health care or farm subsidies — to "pay for" the changes with tax increases or offsetting spending cuts.

The budget suffers, however, from some of the same flaws Democrats see in Bush's February budget plan. Like Bush, the Democrats left out funding for the long-term costs of the war in Iraq and for fixing the alternative minimum tax that threatens unsuspecting middle-class families.

"I don't assert that this is a perfect budget," said Budget Committee Chairman Kent Conrad, D-N.D. "But at the end of the day, the test for us is, 'Can we write a budget for our country?"'