The conclusions were based on e-mail messages and other documents that the committee released on Wednesday. United States policy is to warn companies that they incur risks in signing contracts until Iraq passes an oil law and to strengthen Iraq’s central government. The Kurdistan deal, by ceding responsibility for writing contracts directly to a regional Government, infuriated Iraqi officials. But State Department officials did nothing to discourage the deal and in some cases appeared to welcome it, the documents show.

The company, Hunt Oil of Dallas, signed the deal with Kurdistan’s semi-autonomous Government last September. Its chief executive, Ray L Hunt, a close political ally of President Bush, briefed an advisory board to Bush on his contacts with Kurdish officials before the deal was signed.

In an e-mail message released by the Congressional committee, a State Department official in Washington, briefed by a colleague about the impending deal with the Kurdistan Regional Government, wrote, “Many thanks for the heads up; getting an American company to sign a deal with the KRG will make big news back here. Please keep us posted.”

The release of the documents comes as the administration is defending help that US officials provided in drawing up a separate set of no-bid contracts, still pending, between Iraq’s Oil Ministry in Baghdad and five major Western oil companies to provide services at other Iraqi oil fields.

In the no-bid contracts, the administration said it had provided what it called purely technical help, in writing the contracts. The US played no role in choosing the companies, the administration has said.

Disclosure of those contracts has provided substantial fuel to critics of the Iraq war, both in the US and abroad, who contend that the enormous Iraqi oil reserves were a motivation for the American-led invasion — an assertion the administration has repeatedly denied.

Iraq’s oil minister, Hussain al-Shahristani, has condemned the Kurdistan deal as illegal because it was not approved by Iraq’s Central Government and was struck without an oil law, which has still not been passed. After the deal was signed last year, a senior State Department official in Baghdad criticised it, saying, “We believe these contracts have needlessly elevated tensions between the KRG and the national Government of Iraq.”

The State Department said Wednesday that it had discouraged the deal. Hunt officials declined to comment, and Kurdish government officials said there was no impropriety.