Military chiefs have admitted preparations for war were rushed
A senior British military figure has described the moment that the US "drew back the curtain" on its plans for possible military action in Iraq.
Maj Gen David Wilson, who was UK adviser to US Central Army Command, disclosed the UK was made "privy" to US plans in Florida in June 2002.
The UK later said it could not offer "even basic support" if political and legal hurdles were not cleared.
The Chilcot inquiry is examining UK policy on Iraq between 2001 and 2009.
It is scrutinising the military build-up to the 2003 invasion, looking into when military preparations began in the UK and US and whether they made a diplomatic solution less likely.
Maj Gen Wilson said there was no talk about Iraq by senior US commanders when he first took up his role as the link between UK and US military headquarters in spring 2002.
But he said this "suddenly changed" in June following a meeting between senior UK and US commanders.
In what was a "defining moment", he said the UK was presented with what he described as "options without any commitment" regarding possible military action in Iraq and how the UK might contribute.
"This is when, not just the British but the Australians, were made privy to planning that had gone to that point by the US," he said.
This development raised all kinds of questions in the UK, he said, since British commanders did not know how the US had got to this stage.
"The secure wires went hot," he said of reaction in the UK.
Maj Gen Wilson said he "assumed" the decision to sanction disclosure of the plans was made by then US Defence Secretary Donald Rumsfeld.
In early August, UK and Australian commanders attended a meeting in Florida and were asked to provide what Maj Gen Wilson said were "early observations" on the plans.
He said he advised that "unless political and legal issues are resolved it would be difficult for the UK to deliver even basic support".
He also suggested that other US allies be given insight into the plans and stressed "no decision" was taken on Iraq at that stage.
Earlier, another senior commander said he set up a small "scoping" group in Whitehall to look at potential military options for Iraq in May 2002, not long after a key meeting between Tony Blair and President Bush.
"My job was to bring options," Sir Anthony Piggot, Deputy Chief of the Defence Staff in 2002 said. "There was no talk about plans at that stage. We were talking about options".
November-December: Former top civil servants, spy chiefs, diplomats and military commanders to give evidence
January-February 2010: Tony Blair, Gordon Brown and other politicians expected to appear before the panel
March 2010: Inquiry expected to adjourn ahead of the general election campaign
July-August 2010: Inquiry expected to resume
Report set to be published in late 2010 or early 2011
He said this exercise was driven by an "evolving political intent".
Asked what this intent was, he said he believed it was focused on dealing with the weapons of mass destruction Iraq was believed to possess not regime change.
From an early stage, he believed the minuses of the UK not contributing anything to a potential action "outweighed" the pluses.
Recalling the June 2002 meeting with US commanders which he attended, he said he was told the US had "enough combat power" to go it alone in Iraq but wanted UK support for military and political reasons.
"What we want from the Brits is ideas," he said he was told. "You are the thinkers."
Sir Anthony told the Iraq inquiry that it was never "a stitched-up deal" the UK would be involved in any invasion.
"It was a remarkable logistic achievement to get that force structure in that timeframe into there to play a leading role," he said.
Asked what the UK got out of the mission, he said it showed the UK was a "serious player" and "enhanced no end" its military relationship with the US in terms of future operations and sharing intelligence.
In the first few weeks, the inquiry is hearing from senior diplomats and policy advisers who shaped policy in the run-up to the war.
The crucial question of the legality of the war will not be addressed until early next year, when Tony Blair is expected to give evidence.