When drillers struck oil in a rich new field called Tawke in December 2005, no one but a handful of government and business officials and members of Mr. Galbraith’s inner circle knew that the constitutional provisions he had pushed through only months earlier could enrich him so handsomely.

Image Peter W. Galbraith Credit... Chris Kleponis/Bloomberg News

As the scope of Mr. Galbraith’s financial interests in Kurdistan become clear, they have the potential to inflame some of Iraqis’ deepest fears, including conspiracy theories that the true reason for the American invasion of their country was to take its oil. It may not help that outside Kurdistan, Mr. Galbraith’s influential view that Iraq should be broken up along ethnic lines is considered offensive to many Iraqis’ nationalism. Mr. Biden and Mr. Kerry, who have been influenced by Mr. Galbraith’s thinking but do not advocate such a partitioning of the country, were not aware of Mr. Galbraith’s oil dealings in Iraq, aides to both politicians say.

Some officials say that his financial ties could raise serious questions about the integrity of the constitutional negotiations themselves. “The idea that an oil company was participating in the drafting of the Iraqi Constitution leaves me speechless,” said Feisal Amin al-Istrabadi, a principal drafter of the law that governed Iraq after the United States ceded control to an Iraqi government on June 28, 2004.

In effect, he said, the company “has a representative in the room, drafting.”

DNO’s chief executive, Helge Eide, confirmed that Mr. Galbraith helped negotiate the Tawke deal and advised the company during 2005. But Mr. Eide said that Mr. Galbraith acted solely as a political adviser and that the company never discussed the Constitution negotiations with him. “We certainly never did give any input, language or suggestions on the Constitution,” Mr. Eide said.

When the findings based on interviews by The Times and other research were presented to Mr. Galbraith last weekend, he responded in writing to The Times, confirming that he did work as a mediator between DNO and the Kurdish government until the oil contract was signed in the spring of 2004, and saying that he maintained an “ongoing business relationship” with the company throughout the constitutional negotiations in 2005 and later.

Mr. Galbraith says he held no official position in the United States or Iraq during this entire period and acted purely as a private citizen. He maintains that his largely undeclared dual role was entirely proper. He says that he was simply advocating positions that the Kurds had documented before his relationship with DNO even began.

“What is true is that I undertook business activities that were entirely consistent with my long-held policy views,” Mr. Galbraith said in his response. “I believe my work with DNO (and other companies) helped create the Kurdistan oil industry which helps provide Kurdistan an economic base for the autonomy its people almost unanimously desire.”