"Any agreement will not be considered valid and legal under the current Iraqi law or under the new law," if signed before parliament passes new legislation, he said on the sidelines of an energy conference in Saudi Arabia.

"Therefore, companies should refrain from (signing) any contracts before the new law is passed by parliament and the Federal Council for Oil and Gas can approve those contracts," he told reporters.

The bill, approved by the Shiite-led government in February after months of wrangling, opens Iraq's oil sector to foreign investors.

Under the terms of the draft oil law, Iraq's oil industry will be overseen by a Federal Oil Council and an independent national oil firm.

Revenue will be concentrated in a federal account, and redistributed to provinces on the basis of their populations, which would give the Kurds around 18 to 20 percent of the national cake.

Shahristani hoped the Iraqi parliament would manage to approve the bill before the May 31 deadline.

"It has been sent to parliament. There has been an agreement among political parties to work together to try to pass it before the end of this month," the minister said.

"We still hope parliament will be able to do that ... but with parliament debate, you can never be sure how long it will take," he said.

The Kurdish regional government's oil minister, Ashti Hawrami, said last month that if parliament fails to pass the law by the end-of-May deadline, the Kurds government would award their own contracts.

Iraq, with proven reserves of some 115 billion barrels, has an output of two million barrels per day, but it has the potential to produce much more.