Adnan Mufti, speaker of the parliament, said the Kurdish MPs approved the plan unanimously.

The parliament "approved the suggestion presented by UN representative in Iraq Staffan de Mistura," Mufti said after the parliamentary session.

Last week Nechirvan Barzani, the prime minister of the Kurdish government, said he favoured a six-month extension of the vote on Kirkuk.

According to article 140 of the Iraqi constitution, the referendum had been due to be held by the end of 2007 to decide whether the province of Kirkuk with its oil wealth should go under the control of the northern government.

Barzani said the vote had been delayed "for technical reasons."

He said the six-month extension should be used for a UN-supervised mechanism to sort out the issue of Kirkuk, which sits on the second-largest oil and gas reserves in Iraq.

Kirkuk has been gripped by ethnic tension since the 2003 US-led invasion, with Kurds demanding its incorporation into the autonomous Kurdish region, while Arab and ethnic Turkmen oppose this, fearing they would be marginalised.

Kirkuk was the scene of a massive population upheaval when the then Iraqi president Saddam Hussein staged the forced exile of tens of thousands of Kurds, replacing them with a mainly Arab population from other Iraqi regions.

The city and its province are now claimed by both the Arabs and the Kurds.

Organising the referendum has been made impossible by the lack of any census in the region where the relative weight of each community -- Kurds, Arabs and Turkmen -- is an explosive subject.

The six-month extension is seen as a chance to set up mechanisms under the United Nations to change boundaries and look into relocating populations to undo Saddam's policy.

The Kurds have insisted on a referendum as a condition for their support of the Shiite-dominated central government in Baghdad.

On December 18 US Secretary of State Condoleezza Rice visited Kirkuk in a surprise trip aimed at supporting UN reconciliation efforts.