WASHINGTON — House Speaker John Boehner yesterday ordered House Republicans to “get your ass in line” behind his debt-limit plan — and they did.

Rank-and-file Republicans — including Tea Party conservatives who a day earlier had balked at the less than $1 trillion in spending cuts in Boehner’s plan — began jumping onboard.

The fresh momentum behind the plan comes with just five days left for Congress to approve an increase to the $14.3 trillion debt limit and avert a fiscal disaster.

Boehner (R-Ohio) delivered the stern pep talk to House Republicans at a closed-door meeting yesterday morning and later recounted his remarks on the Laura Ingraham radio show.

The speaker said he couldn’t understand why some conservative Republicans recoiled from his plan.

“Barack Obama hates it, [Sen.] Harry Reid hates it, [Rep.] Nancy Pelosi hates it,” he said.

“The plan we have got on the table is the best opportunity we have to hold the president’s feet to the fire.”

His message resonated with House Republicans, whose initial opposition threatened to undermine Boehner’s bargaining position. He can afford only about two dozen GOP defections when his plan goes to a vote today.

Some will go along reluctantly.

“At the end of the day, it’s nowhere near what I want. It’s not even close to the numbers we want,” said Rep. Mike Grimm (R-SI). “[But] it’s a lot better than what we would have if we let the Senate Democrats and this president continue on this spending spree.”

Rep. Rob Woodall (R-Ga.), a Tea Party-backed freshman member who once had doubts about the Boehner plan, said that “something is better than nothing.”

Boehner was still putting finishing touches on his plan yesterday. It had to be reworked to include more spending cuts after the Congressional Budget Office determined Tuesday that the plan cut just $850 billion over 10 years, not the $1.2 trillion promised.

The plan would initially raise the debt limit by $900 billion to last about six months. A later $1.6 trillion increase would depend on a new congressional committee identifying even more budget cuts to pay for the added debt.

Democrats say the spending cuts disproportionately hurt the poor, seniors and children. In a letter to Boehner yesterday, every Senate Democrat and two independents promised to oppose his plan.

An alternative plan by Senate Majority Leader Harry Reid (D-Nev.) would raise the limit $2.4 trillion, enough to last until after the 2012 elections. But Reid said that his plan, too, was getting “tweaked” after the CBO yesterday reported that it fell about $500 billion short of the promised $2.7 trillion in cuts.

smiller@nypost.com

