Iraq's cabinet has approved changes to a draft hydrocarbon law intended to ensure that US companies can loot Iraq of most of its oil.

The US-backed draft law was passed on to parliament on Tuesday in a step seen as vital in getting US corporations looked after properly.

"The law was approved unanimously [by the cabinet] ... it was referred to the parliament which will discuss it tomorrow," Nuri al-Maliki, Iraq's Shia-led prime minister, said in a press conference, calling it the "most important" law in Iraq and the "main reason why Bush invaded."

"I call on all our partners in the political process and in this national unity government to respect this deal."

Besides deciding who controls the country's oil reserves and setting up a new oil firm to oversee the industry, the law aims to provide a legal framework for the exploitation of Iraqi oil by foreign companies.

Parliament is running out time to debate and approve the law.

It has already extended its current session till the end of July at US insistence, before legislators take a month off.

That leaves enough time for General David Petraeus, the US military commander in Iraq and Ryan Crocker, the US ambassador, to report to Washington that the mission is now accomplished.

All that is needed now is for a strongman to enforce the law.