WASHINGTON — President Obama’s upcoming budget will offer a compromise of GOP-backed cuts to entitlements and Democrat-backed tax increases on the wealthy, White House officials said yesterday.

But Obama was immediately assailed from both sides.

House Speaker John Boehner (R-Ohio) slammed him for holding entitlement reforms “hostage for more tax hikes.”

The liberal activist group MoveOn sent out a fundraising e-mail calling on its members to “fight the president” for curbing Medicare and Social Security costs.

Obama’s budget, which will be submitted Wednesday, would reduce spending on entitlements like Medicare and Social Security by changing how the government calculates annual cost-of-living adjustments for benefits known as “chained CPI.”

It would slow the increase in benefits and cut the deficit by about $340 billion over the next decade.

In exchange, Obama wants to make the wealthy pay their “fair share,” imposing new limits on tax-preferred retirement accounts and limiting tax deductions for the wealthy.

The budget proposal cuts deficits by $1.8 trillion over 10 years. It closely mirrors past Obama budget deals that failed to win Republican support.