Former Iraqi Defence Minister Sultan Hashim Ahmed has been granted immunity from prosecution following his surrender to US forces.
Ahmed surrendered after reported mediation
Mr Ahmed - number 27 on the Americans' list of most wanted former Iraqi officials - gave himself up in the northern city of Mosul last Friday.
White House officials say they have high hopes he will provide significant information on Iraq's alleged weapons programmes.
The news came as US officials indicated that an interim report by the Iraqi Survey Group - charged with locating weapons of mass destruction in the country - would contain no evidence of illegal weapons.
But neither would it close the door on the possibility that such weapons might still be found, they said.
Pentagon officials said the survey group - headed by David Kay, a former UN weapons inspector and now a special adviser to the CIA - had found what they regarded as evidence of Iraqi preparations to produce chemical and biological weapons.
IRAQ SURVEY GROUP
Took over WMD hunt from the US military in June
Using intelligence to build picture of Iraqi weapons programmes
Led by US general, but has some UK and Australian staff
1,300 staff include former UN weapons inspectors
They say there will be enough suspicious evidence uncovered to convince reasonable people that something was afoot.
At present, President George W Bush has more pressing concerns, specifically the cost of the operation in Iraq - a source of ongoing controversy - and the difficulties in getting UN support.
But the BBC's Justin Webb says the issue of weapons of mass destruction may well come back to haunt him.
On Wednesday, a Bush administration source who spoke to the BBC said the interim report - which is likely to be published next month - concludes it is highly unlikely that weapons of mass destruction were shipped out of the country to places like Syria before the US-led war on Iraq.
The Bush administration source told the presenter of BBC television's Daily Politics show, Andrew Neil, that Saddam Hussein had mounted a huge programme to deceive and hinder the work of UN weapons inspectors.
Mr Neil said the report is being finalised and could undergo changes
Mr Neil said that, according to the source, the report will say that the inspectors have not even unearthed "minute amounts of nuclear, chemical or biological weapons material".
Neither have they uncovered any laboratories involved in deploying weapons of mass destruction, not any delivery systems for the weapons.
But, Mr Neil added, the report would publish computer programmes, files, pictures and paperwork which it says shows that Saddam Hussein's regime was attempting to develop a weapons of mass destruction programme.
Mr Neil, a former editor of the British Sunday Times newspaper, stressed he had not seen the draft report, and was reporting what a single source had said its findings were likely to be.
Both the UK Government and the US administration have dismissed the claims as speculation.