Senior US officials and military officers have been interviewed for the Chilcot Inquiry into the Iraq War.
Members of the independent Iraq Inquiry Committee spoke to key players including Paul Bremer - who administrated the country as George Bush's "vice-consul" from 2003-04 - during a series of meetings in Washington and Boston last week.
Others questioned included the former US ambassador to Iraq Ryan Crocker and the leaders of the Iraq Survey Group which conducted a fruitless search for weapons of mass destruction in the aftermath of the 2003 war, David Kay and Charles Duelfer.
As the private discussions, conducted between May 17 and 21, were not formal evidence sessions, transcripts of the conversations will not be published.
A spokesman for the inquiry said that they were intended "to allow the Committee to receive a wider international perspective on the UK's involvement in Iraq over the period being examined by the Inquiry".
The independent inquiry into the UK's involvement in Iraq was commissioned by former Prime Minister Gordon Brown in June 2009 and is expected to report later this year.
Under chairman Sir John Chilcot the inquiry has already taken evidence from witnesses including Tony Blair and Mr Brown himself, but public hearings were suspended during the general election period.
