The provision is part of four so-called annexes that are to be debated with the draft oil law in Parliament. Any objection to one or more of the annexes will stall passage of the law.

“We are worried about these ideas put into the annexes,” Mr. Salih said in an interview in Erbil, the capital of Iraqi Kurdistan. “It worries us a lot.” If the law and the annexes go to a vote before Parliament, a rejection by the Kurdish bloc alone, which holds 58 of 275 seats, would not doom the law. But Parliament operates by consensus, and members say it is almost certain that no law regarding oil will pass without the approval of the Kurds.

A senior Shiite Arab legislator, Sheik Jalaladin al-Saghir, said the concerns raised by the Kurds amounted to a bargaining tactic. “I think it’s a maneuver,” he said, adding that he believed the Kurds “will move forward to pass the law since everybody needs it.”

Contributing a further layer of complication, a Sunni Arab legislator said Wednesday evening that the main Sunni Arab bloc, which has 44 legislative seats, objected to any discussion of the law in Parliament at this time. “Acceleration in presenting it is inappropriate since the security condition is not encouraging,” said the legislator, Saleem Abdullah. He said Sunni Arabs were also worried that the law would give foreign companies too large a role in the country’s oil industry. Sunni Arab political leaders supported cabinet approval of the draft law, but appear ambivalent now.

White House officials have said passage of the oil law is one of four major benchmarks they would like the Iraqi government to meet before fall.

During a visit to Baghdad last month, Defense Secretary Robert M. Gates told the Iraqi prime minister, Nuri Kamal al-Maliki, that Mr. Bush would weigh Iraq’s commitment to meeting the goals when he decided at the end of the summer whether to extend the recent troop increase.

Differences on benchmarks for the Iraqi government are a central issue in the spending-bill talks between Mr. Bush and Democrats. Democrats, conceding they are unable to use the bill to force the withdrawal of troops, hope to write new benchmarks into the legislation, with consequences if the goals are not met.