Iraq's most wanted man - he has a US$25 million (HK$195 million) bounty on his head - also purportedly vowed to head to the Palestinian territories to continue the fight after ``victory'' had been achieved in Iraq.

``The enemy is experiencing its worst days on the soil of Mesopotamia, at a time when a member of the US Congress has said the United States is losing the war in Iraq,'' said the voice message on an Internet site, without giving further explanation.

``Some people want to stop our jihad in Mesopotamia,'' the voice said, referring to contacts that have taken place between insurgents in Iraq and US officials.

It was not possible to verify the authenticity of the message, which came two days after a newly named ``spokesman'' for two Iraqi insurgent groups asked the US Congress to make an ``official'' offer for negotiations.

US Defense Secretary Donald Rumsfeld has confirmed that contacts have taken place between Washington and elements from the insurgency - and also made clear that US officials had never talked with Zarqawi.

Zarqawi, whose insurgency is operated by mainly Sunni militants, said he was creating a new brigade, called ``Brigade Omar'' to take on its opponents within Iraq's majority Shiite Muslim community.

The new brigade would ``seek to remove the symbols and the members of the brigades of treason, the Badr Brigades,'' referring to the thousands-strong Shiite paramilitaries trained and supported by Iran to fight the former regime.

Its parent organisation, the Supreme Council of the Islamic Revolution in Iraq, says it has now been transformed into a political organization called the Badr Organization.

Hours after the message was made public, a lieutenant-colonel in the Badr militia was gunned down in Baghdad, the defence ministry said.

In the new recording, Zarqawi for the first time also vowed to move ``after the victory in Iraq'' into the Palestinian territories to continue the jihad there.

``All that we want is to win a victory in Iraq so that we can go into Beit Al-Maqdes [Jerusalem].''

The voice also hit out at some Islamist ideologues, like his ex-mentor Abu Mohamad al-Madqissi, who have slammed the insurgency for targeting ordinary Iraqis as well as the international forces based in Iraq.

He lambasted clerics for making distinctions between ``honorable'' and ``dishonorable'' jihad while staying well clear of fighting themselves.