Tony Blair’s advisers privately questioned if the US had “proper political control” of military operations in Iraq after a senior US official confided that George W Bush believed he was on a “mission from God” against Iraqi insurgents, newly released documents reveal.

Blair needed to “deliver some difficult messages” to the then US president for a “more measured approach” in April 2004, following a US military operation to suppress a major uprising in the city of Falluja, according to papers released to the National Archives in Kew, west London.

In a surprisingly candid conversation, recorded in a document marked “please protect very carefully”, Richard “Rich” Armitage, then US deputy secretary of state, told Sir David Manning, then UK ambassador, that Bush had needed a “dose of reality” after demanding US forces “kick ass” in Falluja, where US troops were engaged in a bloody battle with Iraqi militants after four private military contractors were ambushed and killed.