'If there is no change in three months, there will be war again'

A crucial Iraqi ally of the United States in its recent successes in the country is threatening to withdraw his support and allow al-Qa'ida to return if his fighters are not incorporated into the Iraqi army and police.

"If there is no change in three months there will be war again," said Abu Marouf, the commander of 13,000 fighters who formerly fought the Americans. He and his men switched sides last year to battle al-Qa'ida and defeated it in its main stronghold in and around Fallujah.

"If the Americans think they can use us to crush al-Qa'ida and then push us to one side, they are mistaken," Abu Marouf told The Independent in an interview in a scantily furnished villa beside an abandoned cemetery near the village of Khandari outside Fallujah. He said that all he and his tribal following had to do was stand aside and al-Qa'ida's fighters would automatically come back. If they did so he might have to ally himself to a resurgent al-Qa'ida in order to "protect myself and my men".

Abu Marouf said he was confident that his forces controlled a swath of territory stretching east from Fallujah into Baghdad and includes what Americans called "the triangle of death" south-west of the capital. Even so his bodyguards, armed with AK-47 assault rifles, nervously watched the abandoned canals and reed beds around his temporary headquarters. Others craned over light machine guns in newly built watch towers. Several anti-Qa'ida tribal leaders have been killed by suicide bombers in recent weeks.

His threat is highly dangerous for the US and Iraqi government, neither of which made any headway in ending the Sunni insurgency against the US occupation for four years until the tribes of Anbar, the province in which Fallujah lies, turned against al-Qa'ida. They formed the Awakening movement, known in Arabic as al-Sahwah, of which Abu Marouf, whose full name is Karim Ismail Hassan al-Zubai, is a leading member.

The Iraqi Foreign Minister, Hoshyar Zebari, warned last week it would be "very dangerous" if the Awakening movement's 80,000 fighters were not absorbed into the army and police. "They are not that well organised and could easily be manipulated by al-Qa'ida," he said.

The Iraqi government fears ceding power to the Awakening movement which it sees as an American-funded Sunni militia, whose leaders are often former military or security officers from Saddam Hussein's regime and are unlikely to show long-term loyalty to the Shia and Kurdish-dominated administration.

Abu Marouf – a thin man aged about 40, with a short beard and wearing a brown suit and lilac tie – says he was "security officer" before the US invasion of 2003. Afterwards he became a resistance fighter and, though he will not say which guerrilla group he belonged to, local sources say he was a commander of the 1920 Revolution Brigades. He is also a member of the powerful Zubai tribe that was at the heart of anti-American resistance in an area which saw the fiercest fighting during the Sunni rebellion against the occupation.

He has a precise memory for dates and figures. He says that he started secretly working against al-Qa'ida at a meeting as long ago as 14 April 2005. He and his men gathered intelligence. Eight months later they started making attacks on al-Qa'ida, which was trying to monopolise power in Sunni areas.

"They cut off people's heads and put them on sticks, as if they were sheep. They cut off my brother's head with a razor. Thirteen of my relatives and 450 members of my tribe were killed by them," he said.

Part of Abu Marouf's force is paid for by the Americans. Ordinary fighters are believed to receive $350 (£175) a month and officers $1,200, but some receive no salary. He makes clear that he wants long-term jobs for himself and his followers and that "they must be long-term jobs". There is more than just money involved here. The Sunni tribal leaders want a share of power in Baghdad which they lost when Saddam Hussein was deposed.

The US calls the Awakening movement groups "Concerned Citizens", as if they were pacific householders heroically restoring law and order. In fact, the US has handed over Sunni areas to the guerrilla groups such as the 1920 Brigades and the Islamic Army who have been blowing up American solders since 2003.

This creates a serious problem for the Iraqi government and for the Americans themselves. Though Abu Marouf wants to join the government security forces, he volunteers that he considers the present Iraqi government of Nouri al-Maliki "the worst government in the world – his army has got 13 divisions, most of which are recruited from Shia militias controlled by Iran."

It is clear that Abu Marouf sees the Shia religious party takeover of government as something to be resisted.

The city of Fallujah – many of its buildings still in ruins since the US Marines stormed it in November 2004 – is peaceful compared with six months ago. Al-Qa'ida fighters, who once dominated it, have either gone or are keeping a low profile. The Americans have a large military camp on its outskirts. But the defeat of al-Qa'ida is not exactly a victory for the Iraqi government.

In the centre of the city is a much-attacked police station run by Colonel Feisal Ismail Hassan al-Zubai, an authoritative looking man, who is the elder brother of Abu Marouf. A career officer in Saddam Hussein's Special Forces since 1983, who fought in 11 battles against Iran, he was appointed police chief in December 2006. When I asked what he did previously he said: "I was fighting against the Americans." Asked why had he changed sides he replied: "When I compared the Americans to al-Qa'ida and the [Shia] militia, I chose the Americans."

Beside Colonel Feisal is a gold framed picture of himself as a young officer. "That was when I was a lieutenant in the real Iraqi army," he says. Behind him is the old Iraqi flag which the government is trying to replace.

He says: "The worst day of my life was when Saddam Hussein fell in 2003." He chokes himself off from giving an account of the first battle of Fallujah against the Americans in April 2004 in which he appears to have played a role. "The Americans now give me everything I want," he says.

There is no doubt that Abu Marouf and Colonel Feisal are far better people than the savage sectarian bigots of al-Qa'ida whom they have driven away.

But, far from America having won a victory in Iraq, violence has fallen largely because the United States has handed power to the guerrillas who fought it for so long.

If the Iraqi government pretends it has conquered its enemies and refuses to give men like Abu Marouf a share in power then Iraq will soon being facing another war.