The Senate approved an amendment Tuesday to extend an investigative office that unearthed millions of dollars in waste and fraud associated with the rebuilding of Iraq.

The amendment, passed by voice vote as part of the military construction and veterans' spending bill, would keep the inspector general's office running through October 2008. Under current law, it will expire in October 2007.

The amendment was offered by Republican Susan Collins, the chairwoman of the Homeland Security and Governmental Affairs Committee, and Wisconsin Democrat Russ Feingold.

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"That office has been enormously effective as a watchdog," Collins said in a telephone interview. "It's inconceivable to me that we would allow it to expire prematurely when literally billions of dollars are still being spent on Iraqi reconstruction projects."

The overall spending bill was expected to pass Tuesday night or Wednesday.

Connecticut Sen. Joseph Lieberman, who will become chairman of the committee when Democrats take over the Senate next year, called the office "critically necessary."

"And it's delivered — often to our consternation," he said at a new conference with Collins, Feingold and Sen. Norm Coleman, R-Minn.

"This is something that has actually gone right," said Feingold, a harsh critic of the war. "And it would be a real serious mistake to undo it prematurely."

Led by Stuart Bowen Jr., the Office of the Special Inspector General for Iraq Reconstruction tracks spending in the multibillion-dollar effort to rebuild Iraq.

The agency's work has resulted in four criminal convictions and, most recently, evidence that a Halliburton subsidiary exploited federal regulations to hide details on its contract performance.

"Until taxpayer dollars are finished being spent in Iraq, we need oversight," said Coleman.

Earlier this year, Collins pushed through the Senate a measure that would allow the agency to review more than $6 billion in additional funding aimed at stabilizing Iraq — in effect keeping the IG office in business.

But that provision, added to a major defense bill, was stripped from the final legislation when it was negotiated with Rep. Duncan Hunter, chairman of the House Armed Services Committee.

Hunter did not return phone and e-mail messages seeking comment Tuesday. In a statement a couple of weeks ago, he said he agreed the office had been useful but that a termination date was needed.

Setting the 2007 date "ensures that we have a smooth transition from the special inspector general to the inspectors general of State and Defense," Hunter said in that statement.

Collins said she didn't think the latest provision would face similar obstacles when House and Senate negotiators finalize the military construction and veterans' spending bill.

"I don't think so, now that this issue has been exposed to the light of day, there has been a groundswell of support for retaining the office," she said. "And I'm very hopeful that the Congress will act promptly to extend the office."

Complete coverage is available in FOXNews.com's Iraq Center.