The Senate is to begin debate Tuesday on an emergency supplemental bill for Iraq and Hurricane Katrina relief that is expected to be loaded down with pet projects, border security and gas price amendments.

In February, President Bush requested $91 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 a $92 billion measure, close to the president's request. But by time the Senate gets to debate it, the total cost of the bill will be $106.5 billion, nearly $15 billion over the president's original request, and that figure could grow as more amendments are offered.

The White House, itself — despite its own concerns about the measure's spiraling cost — plans to ask as early as Tuesday for another $2 billion to repair and strengthen levees in and around New Orleans. Press Secretary Scott McClellan didn't balk on Monday when asked about an amendment by Sen. Judd Gregg, R-N.H. and endorsed by Majority Leader Bill Frist, R-Tenn., that will add to the bill $2 billion in new border security funds.

"We want to see them move forward on that in a way that meets important priorities, and that is done so in a fiscally responsible way," McClellan said. "We want to make sure that our troops have the resources they need, and that's why it's important to act quickly on the spending legislation. We want to make sure that we continue to support the people along the Gulf Coast as they're rebuilding their communities."

Immigration reform is likely the first issue to be addressed after the supplemental bill is finished. Lawmakers are looking for a compromise that would create a guest worker program and protect the border. Gregg's amendment would make sure the security element is not neglected in the future by allocating money in the emergency supplemental bill to hiring and training more Border Patrol agents and building new detention centers for immigrants caught entering the country. The funding would also be used to buy helicopters to patrol the U.S-Mexico border and to erect more fencing along parts of it.

But Gregg's amendment isn't without offsets. He also is proposing to cut a different section of the bill that gives money to an Army effort to restructure combat units. He said the Army funds can be addressed in the regular defense budget and not in the supplemental.

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, including grants to states to build and repair housing and $2.1 billion for levees and flood control projects.

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.

That has concerned fiscal conservatives — 19 Republicans voted against the House version — but many of the measures added to the Senate version already have the backing of the Appropriations Committee. They include $4 billion for farmers hit by drought, floods and high energy costs, $2.3 billion to combat the avian flu and $1.1 billion in aid for Gulf Coast fisheries.

The bill is also generous to Mississippi, home to Appropriations Committee GOP Chairman Thad Cochran, and badly hit by Hurricane Katrina. Probably the most controversial provision would provide $700 million to purchase a Mississippi freight rail line and give it to the state for a new coastal highway. The rail was damaged badly during Katrina but a $300 billion payout by insurance paid for the cost of repairs.

Sen. Tom Coburn, R-Okla., has vowed to force the Senate to vote on dumping the Mississippi project, which critics say was a long-held desire by Cochran and GOP Gov. Haley Barbour before Katrina hit. Coburn likened the deal to last year's "bridge to nowhere," a $223 million project — shelved after it drew scorn from the media and the public — connecting Alaska's lightly populated Gravina Island to Ketchikan.

The bill also contains a boon for Northrop Grumman, which owns the Ingles Shipyard in Pascagoula, Miss. The yard sustained damage from Katrina and Northrop Grumman is insured for the "business disruption" costs of the hurricane. The issue is now in court.

Cochran, however, added a provision to require the Navy to pay Northrop Grumman immediately, and costs could hit $500 million. Taxpayers would be repaid with proceeds from any insurance settlement, but there's no guarantee of that.

On top of it, Democrats are likely to offer an amendment to add to the already rapidly growing budget for veterans' medical care. And the issue of skyrocketing gasoline prices seems sure to find its way into the debate, though plans are as yet unclear.

"This week, the supplemental appropriations bill is on the floor. It is important legislation, especially since President Bush refuses to put the costs of the war in Iraq or the costs of helping Katrina’s victims his budget, so he can hide the costs and his horrible fiscal record," said Senate Minority Leader Harry Reid, D-Nev., on the Senate floor Monday.

"In spite of the president’s budget gimmicks, Democrats look forward to the debate on the supplemental. We have a number of tough and smart amendments that we will offer to protect the American people, address the situation in Iraq and provide relief from the energy crisis at home," Reid said.

Bush is expected to meet Tuesday with lawmakers from both parties and both chambers of Congress on Iraq and immigration. It is unclear whether those meetings will sway an official policy statement expected from the White House Tuesday that some conservatives hope will give Bush an opportunity to make a stern threat to veto the measure over its cost.

FOX News' Sharon Kehnemui Liss and The Associated Press contributed to this report.