Updated

At the request of Senate leadership, President Bush is issuing a veto threat against the emergency supplemental bill currently being debated in the Senate. The president has not yet vetoed a bill since taking office in 2001.

The Office of Management and Budget issued a statement late Tuesday that if the $92.2 billion cost of the bill is exceeded, Bush will veto the emergency spending measure for U.S. forces in Iraq and Hurricane Katrina relief, among other items.

"The Senate reported bill substantially exceeds the president's request, primarily for items that are unrelated to the GWOT (global War on Terror) and hurricane response. The administration is seriously concerned with the overall funding level and the numerous unrequested items included in the Senate bill that are unrelated to the war or emergency hurricane relief needs. The final version of the legislation must remain focused on addressing urgent national priorities while maintaining fiscal discipline," reads the statement of administration policy.

"Accordingly, if the president is ultimately presented a bill that provides more than $92.2 billion, exclusive of funding for the president's plan to address pandemic influenza, he will veto the bill," the statement continues.

In February, President Bush requested $92.2 billion to pay for the war in Iraq and cleanup efforts in the Gulf Coast as a result of last September's hurricane. In March, the House voted overwhelmingly for the measure, and came in just under the president's request. But by time the Senate started debating it on Tuesday afternoon, the total cost of the bill had already approached $106.5 billion, more than $14 billion over the president's original request. That figure could grow as more amendments are offered.

Republican fiscal conservatives in the Senate have voiced concern in recent days over the supplemental's runaway excess, and one outspoken critic, Sen. Tom Coburn, R-Okla., and other deficit hawks have taken particular issue with several earmarks in the bill, most especially the so-called "rail to nowhere." Pushed by Mississippi Sens. Trent Lott and Thad Cochran, an amendment requests that a particular rail line be moved away from the Gulf Coast and built further inland where it will be safe from future storms like Katrina. The rail line, however, was already repaired after the hurricane, and insurance proceeds paid the tab.

Among the changes to the bill, the president sent a request to House Speaker Dennis Hastert asking him to give the Army Corps of Engineers $2.2 billion to aid recovery, but the money is being offset from money already appropriated in the House bill to the Federal Emergency Management Agency's Disaster Relief Fund. However, the money removed from FEMA's coffers will have to be refilled again in the fall instead of next year if the amendment is approved.

Sen. Judd Gregg, R-N.H., also was offering an amendment to the supplemental for $2 billion in new border security funds, but the money, he said, was also being offset by money that was intended to go to the Army to restructure its combat units. He said the Army funds can be addressed in the regular defense budget and not in the supplemental.

"Border security must receive the same attention as other aspects of national security, and that means committing resources," Gregg said.

The version of the bill that the Senate will take up starts by giving $67.6 billion to Pentagon war operations and $27.1 billion to hurricane relief. To date, Congress has provided about $315 billion for the war in Iraq, and the latest addition, combined with the total 2006 fiscal year spending, would add another $117 billion to this year's effort. The response to hurricanes Katrina and Rita so far total $87.5 billion.

The add-ons include $4 billion for farmers hit by drought, floods and high energy costs, $2.3 billion to combat bird flu and $1.1 billion in aid for Gulf Coast fisheries.

Democratic senators, hoping to get credit for addressing the rising gas prices, offered amendments that are meant to punish oil companies. One amendment by Sens. Chris Dodd of Connecticut and Byron Dorgan of North Dakota would give Americans a rebate when gas rises above $40 per barrel. The money would come from a a 50 percent windfall profits tax imposed on oil company revenue derived from sales of oil at more than $40 per barrel.

Another amendment by Sen. John Kerry of Massachusetts would repeal "the president's earlier tax giveaways for oil companies."

Sen. Bob Menendez, D-N.J., said he will offer a plan to suspend the 18.4 cents-per-gallon gasoline tax for two months, with its cost financed by reducing tax breaks for the oil industry.

Conservatives such as Craig Thomas, R-Wyo., vow to try to trim the bill back to Bush's $92.2 billion request.

"The original request was far from pocket change," Thomas said. "And yet, we apparently felt compelled to add significant new spending."

Turning the tables on the national security debate, one senior Democratic leadership aide told Fox News that Bush's veto threat on the wartime supplemental is "reckless and a gross miscalculation."

FOX News' Carl Cameron and Trish Turner and The Associated Press contributed to this report.