The two have been at odds over Maliki's plans to amend the constitution to clear the way for a stronger central government in Baghdad at the expense of the powers of Barzani's administration based in the northern city of Arbil.

In a speech to students in the Kurdish town of Dohuk, Barzani did not refer to the premier by name, but his allusion was fairly plain.

"We know that there is someone who wants to restore dictatorship in Iraq through control of the army and police," the Kurdish leader said.

"If amendments to the constitution are aimed at improving things, then there's no problem. But we will never accept them if the aim is to place restrictions on Kurdish interests."

The autonomous Kurdish region will not be holding provincial elections with the rest of Iraq on January 31. Nor will the disputed oil province of Kirkuk which Barzani is determined to incorporate into his autonomous region.

But in a campaign speech in the Shiite town of Diwaniyah south of Baghdad, Maliki warned that some in Iraq were seeking to break away.

"I want to tell those who have ambitions to create a micro-state that our attachment to the constitution has allowed us to unify Iraq," he said, again without naming names.

Barzani has repeatedly denied the charge of separatism.

"We are not calling for secession of any part of Iraq. We want the nation's unity and integrity, but through democratic means," he said in a speech last Monday.