An Iraqi-born American citizen pleaded guilty Tuesday to several charges as part of the federal investigation into the U.N. Oil-for-Food (search) program, becoming the first person to be convicted in the growing scandal.

Attorney General John Ashcroft announced the agreement with Samir Vincent (search), accused of being an unregistered Iraqi agent between the first and second Persian Gulf wars.

"Combatting corruption, such as that detailed in this plea agreement, sends a clear message both to American citizens and citizens of Iraq: corruption will not be tolerated. It will be prosecuted," Ashcroft said.

Vincent, of Annandale, Va., pleaded guilty to making false statements on income-tax returns, acting as an unregistered agent of a foreign government and violating the International Emergency Economic Powers Act (search). He could be sentenced to 28 years in prison.

Vincent is cooperating with the "active and ongoing probe of fraud and abuse in the U.N. Oil-for-Food program," Ashcroft said at a news conference.

The case is being handled by the U.S. Attorney's Office in New York. The criminal indictment and plea deal were filed in federal court in the Southern District of New York. Read the indictment by clicking here (pdf).

The Justice Department is also investigating U.N. Secretary-General Kofi Annan's son, Kojo Annan.

In a statement in federal court in New York on Tuesday, Vincent said that in 1996 during negotiations on the Oil-for-Food program some Iraqi government cash was given to a person "whom I understood was a United Nations official."

Court documents say only that this unspecified payment went to "another individual" to satisfy an agreement regarding the pro-Iraqi effort to influence the U.N. resolution creating the program.

Vincent received, apparently legally, five separate allocations of Iraqi oil vouchers under Oil-for-Food, partly as compensation for lobbying efforts. He reaped profits totaling millions of dollars by selling those five allocations to an oil company, the Justice Department said.

According to court papers, Vincent was one of only three American citizens allowed to profit by selling Iraqi oil or the options to trade it.

But as an American citizen in the employ of a foreign government, Vincent was required to register as a foreign agent. He also may have neglected to report some or all of the profits made by selling oil vouchers to the Internal Revenue Service.

The Justice Department said that from 1992 to 2003, Vincent consulted with Saddam Hussein's government about efforts to loosen or end the United Nations sanctions imposed upon Iraq after the 1991 Gulf War.

He was also involved in the drafting of the Oil-for-Food program, including agreements guaranteeing himself and others "millions of dollars in compensation."

Vincent got instructions in 1995 and 1996 from high-level Iraqi officials, and carried those instructions out in meetings with U.N. officials, Justice officials said.

During that period, Vincent never registered with the federal government as an agent of the Iraqi government.

Yet between 1998 and 2003, Vincent lobbied former U.S. officials close to both the Clinton and Bush administrations in an unsuccessful attempt to soften U.S. policy toward Iraq.

He then reported on his meetings to the Iraqi Intelligence Service and other Iraqi officials.

In particular, Iraqi intelligence officials sent a message to Vincent that he was to relay to a former U.S. official regarding Iraq's position on re-admitting weapons inspectors in return for the repeal of sanctions.

Vincent's name was listed in the Iraq Survey Group (search) report released by the CIA in October 2003, which cited the Oil-for-Food scandal extensively in its discussion of Saddam Hussein's schemes.

According to the report, Vincent's company, Phoenix International, was awarded vouchers for 1.5 million barrels of oil in 1999 and 2000, which Vincent sold for $1 million.

In total, Vincent and Phoenix received vouchers for 7.9 million barrels of oil, realizing a profit of $3.6 million, between 1997 and 2001, according to the report.

Click here to read the report's key findings or click here to read the main volume of the report (both pdf).

In a faxed statement to FOX News in October, Vincent said Phoenix legally received oil vouchers under the program.

In 2000, Vincent led Iraqi religious leaders on a tour of the United States to push for an end to Iraqi sanctions. Among the people the group met with was former President Jimmy Carter. Vincent worked with the Rev. Billy Graham on that tour.

The topic of Oil-for-Food spilled Tuesday into the Senate confirmation hearing of Condoleezza Rice, who President Bush nominated to be the nation's next secretary of state.

"I think it is a scandal what happened with Oil-for-Food," she said in response to a question from Sen. Norm Coleman, R-Minn., who is leading one of the five congressional investigations into the program.

Rice said the United States relied on Oil-for-Food "to keep Saddam Hussein contained and checked. And clearly we weren't doing that. The sanctions were breaking down. He was playing the international community like a violin."

Besides the congressional focus on the topic, the United Nations also approved an investigation headed by Paul Volcker, a former chairman of the Federal Reserver. Volcker's panel is expected to release an interim report into Oil-for-Food later this month.

On Tuesday, Volcker released a statement saying that his group — known as the Independent Inquiry Committee — was "fully aware" of Vincent's involvement with Oil-for-Food.

"For a considerable period of time we have been in discussions with the U.S. Attorney's Office for the Southern District of New York in an effort to interview Mr. Vincent and obtain his assistance in the IIC's investigation. It is hoped that today's developments will allow us to meet that objective as soon as possible," the statement said.

FOX News' Catherine Herridge and Anna Persky and The Associated Press contributed to this report.