WASHINGTON (AFP) - Former US president George W. Bush reiterated his belief on Wednesday that the world is "better off" without Saddam Hussein, as a damning inquiry blasted Britain's part in the rush for war with Iraq in 2003.

"Despite the intelligence failures and other mistakes he has acknowledged previously, President Bush continues to believe the whole world is better off without Saddam Hussein in power," Bush's spokesman Freddy Ford said in a statement.

"He is deeply grateful for the service and sacrifice of American and coalition forces in the war on terror. And there was no stronger ally than the United Kingdom under the leadership of Prime Minister Tony Blair."

Britain's former prime minister was at the centre of a detailed inquiry that probed Britain's role in the US-led war, examining the flawed intelligence, questionable legal basis and "woefully inadequate" preparation for the occupation.

Britain deployed troops before diplomatic options had been exhausted, the report said.

Broader reaction to the lengthy inquiry by John Chilcot was muted in the United States, with officials unwilling to weigh in on historical decisions.

President Barack Obama's "longstanding opposition to the invasion of Iraq is well known and has been extensively litigated," White House spokesman Josh Earnest said.

Obama "has been dealing with the consequences of that fateful decision for the entirety of his presidency. Future presidents will likely have to do the same," he added.

"It is important that the United States... learn the lessons of those past mistakes."

John Kirby, a spokesman for Secretary of State John Kerry, said the current administration is focused on the current crises in Iraq and Syria.

"Our focus is on trying to get a political transition in Syria, trying to defeat Daesh (the Islamic State group) in Iraq and Syria; trying to help Prime Minister (Haider al-)Abadi make the necessary political and economic reforms he knows he needs to make in his country," he said.

"That's where Secretary Kerry's head is, and we're not interested in re-litigating the decisions that led to the Iraq war in 2003." Defence Secretary Ashton Carter declined to comment on the Chilcot report.