House leaders delayed a vote on a Republican U.S. debt reduction plan after congressional budget officials said it would save $150 billion less than advertised. The non-partisan Congressional Budget Office said House Speaker John Boehner's plan would cut spending $850 billion over a decade, not $1 trillion as he said it would. The budget office conclusion Tuesday night capped a day in which the Ohio Republican's plan faced a barrage of conservative criticism that the cuts were not nearly deep enough. Four Republican senators with Tea Party links wrote to their House colleagues urging them to vote against the measure. The Club for Growth -- which advocates limited government, lower taxes and less government spending, while scoring lawmakers on their fiscally conservative votes -- also came out against the plan. So did other conservative groups including the Heritage Foundation and a national coalition of Tea Party groups, The New York Times reported. In addition, Senate Majority Leader Harry Reid, D-Nev., called it "dead on arrival in the Senate, if they get it out of the House." And the White House said President Barack Obama would veto the bill if it reached his desk. Boehner's congressional staffers planned to work through the night to rework the measure to achieve the amount of cuts originally pledged, Boehner's office said Tuesday night. The Times said it was possible the congressional staffers would simply reduce the debt-limit increase to just under $850 billion to match the smaller budget cuts -- a move the newspaper said would make the deal even less palatable to Democrats. Boehner presented a two-stage deficit-reduction plan Monday that would let the $14.3 trillion federal debt limit rise immediately by about $1 trillion in exchange for $1.2 trillion in spending cuts over 10 years. Those were the cuts the Congressional Budget Office said would actually amount to $850 billion. Boehner's plan tied a second increase early next year to the ability of a proposed new bipartisan congressional committee to produce more reductions. His plan is expected to come up for a vote Thursday. Reid has not brought his own debt legislation to the floor because he wanted to see how Boehner's measure fares, aides said. Reid's proposal would raise the debt ceiling through 2012 and cut $1.2 trillion from federal agency budgets and recurring programs such as agriculture subsidies. Like some earlier Republican plans, the plan counts about $1 trillion in savings from ending U.S. military combat involvement in Iraq and Afghanistan. But House Republicans say counting money not spent on a war the nation is already planning to end is a budget gimmick. The Obama administration and a number of Democratic and Republican economists says the nation will risk defaulting on its bills Aug. 2 if the debt limit isn't raised before then. Those defaults could include federal healthcare and retirement benefits, military salaries and payments due to investors, the administration says. Credit-rating companies threaten to downgrade the nation's AAA rating, which could drive up interest rates for ordinary citizens and state and local governments as well as the federal government, officials said. Some Republicans assert the administration is exaggerating the economic fallout for political gain. Several Wall Street banks and a Washington research organization say Washington actually won't default until Aug. 10, due to an inflow of tax payments and maneuvering by the U.S. Treasury Department, the Times said. White House spokesman Jay Carney stuck to the Aug. 2 deadline in response to the news story. If true, the additional eight days could provide potentially critical breathing room for Congress to raise the debt ceiling, the Times said.