A jury will be left to decide whether Oscar Wyatt Jr. is an opportunistic businessman who illegally paid kickbacks to Saddam Hussein’s regime for oil deals or an American hero who tried to avert the war with Iraq.

Jurors, after opening statements were presented today, will see Iraqi documents and bank records from around the world and hear testimony from two former Iraqi oil officials as prosecutors seek to show Mr. Wyatt conspired with others to pay millions of dollars in kickbacks to secure deals, Assistant U.S. Attorney Stephen Miller said.

A defense lawyer, Gerald Shargel, promised to prove his client is a World War II hero who built an oil fortune from an initial $800 investment, gaining such wisdom about the oil industry and the Middle East that he befriended American leaders from President Kennedy to President Clinton, who once wrote to him: “Keep those ideas coming, Oscar.”

“This case is about the United States at its hypocritical worst,” Mr. Shargel said, noting that Mr. Wyatt, 83, a lifelong Democrat and had clashed with the Bush administration, pleading with officials not to go to war in 2003.

Mr. Shargel said Mr. Wyatt had provided information about events and people in Iraq to an American agency between 1978 and 1989, though he did not identify the agency. He said Mr. Wyatt was a friend and confidant of President Nixon and President Reagan.

“Time and time again, he showed his loyalty to this country,” Mr. Shargel said. “His heart was an American heart. His loyalty was to the United States. His patriotism was unwavering.”

Mr. Miller, the prosecutor, accused Mr. Wyatt of secretly obtaining oil from Iraq in the 1990s after Iraq’s invasion of Kuwait and the Gulf War led to sanctions meant to isolate Iraq from the rest of the world.

“When the world imposed sanctions on Iraq, Oscar Wyatt stepped up to help them evade sanctions,” Mr. Miller said.

He said the U.N. oil-for-food program became corrupted in 2000 when Iraqi officials began demanding illegal surcharges in return for contracts to buy Iraqi oil.

He said Mr. Wyatt used the contacts he had in the 1990s to pay millions of dollars in surcharges to Iraq, part of hundreds of millions of dollars that Iraq collected illegally that should have gone to Iraqis for humanitarian needs.

Mr. Shargel said Mr. Wyatt had nothing to do with the corrupt nature of the oil-for-food program, flawed American policy toward Iraq, and the dependence of Americans on Middle East oil.

“Oscar Wyatt did not pay any surcharge to the Iraqis,” Mr. Shargel said. “Oscar Wyatt did not break the law.”

He told jurors Mr. Wyatt flew American oil workers out of Iraq when Saddam was seeking to keep them as hostages before the first Gulf War. He said jurors will hear a tape of Saddam speaking through an interpreter at a meeting as Mr. Wyatt urged the Americans be freed.

The trial before U.S. District Judge Denny Chin is expected to last four to six weeks.

Mr. Wyatt, who could face more than 60 years in prison, has been free on bail since he was charged with conspiring with others to gain favored status for oil contracts by providing money and equipment to the former government of Iraq between 1994 and March 2003.

The oil-for-food program, which ran from 1996 to 2003, was created to help Iraqis cope with U.N. sanctions imposed after Saddam’s 1990 invasion of Kuwait. It let the Iraqi government sell oil primarily to buy humanitarian goods.