Giving a blunt and extraordinarily candid assessment, he also said that the Pentagon had clearly sent too few troops to stabilise the country after the removal of Saddam Hussein. Mr Gates’s critique of Washington’s fortunes on the ground contradicted directly Mr Bush’s claim last week that “absolutely we are winning” in Iraq.

His veiled criticism of troop levels was a swipe at Donald Rumsfeld, whom he has replaced at the Defence Department. In doing so, Mr Gates, 63, made clear, on the opening day of his confirmation hearings, that he would approach the job of Defence Secretary as his own man. He would speak “frankly and boldly” to the White House and Congress about the problems facing the US in Iraq, he said: “I can assure you that I don’t owe anybody anything.”

Asked by Senator Carl Levin, a Democrat, whether the US was winning the war in Iraq, he replied: “No, sir.” Mr Gates rejected any idea of a “stay the course” strategy, telling the senators that the status quo in Iraq was unacceptable. “What we are doing now [in Iraq] is not satisfactory,” he said.

In his opening remarks, he emphasised that Iraq would be his highest priority, adding: “While I am open to alternative ideas about our future strategy and tactics in Iraq, I feel quite strongly about one point: developments in Iraq over the next year or two will shape the entire Middle East and greatly influence global geopolitics for many years to come.”

Mr Gates added that the next year or two would decide “whether the next president will face a slowly but steadily improving situation in Iraq and in the region, or will face the very real risk, and possibly reality, of a regional conflagration”.

The contrast to Mr Rumsfeld, whose obfuscation when giving congressional testimony dismayed both Democrats and Republicans, was stunning. His confirmation will be rapid.

Already last night Mr Gates won the unanimous endorsement of the Senate’s Armed Services Committee. “What we expect is forthrightness and truth and Gates clearly has the message,” said Bill Nelson, a Democrat Senator.

Mr Gates, who was CIA director when Mr Bush’s father was President, is known as a foreign policy realist who in recent years has advocated direct negotiations with Iran.

He comes from a circle of foreign policy advisers who counselled the first President Bush between 1989 and 1992. That team also included James Baker, whose Iraq Study Group will report today with recommendations on how to navigate the US out of the war.

Mr Gates will arrive at the Pentagon amid intense pressure on Mr Bush and his military chiefs to take a new approach in Iraq, where nearly 3,000 American lives have been lost.

Like the President, Mr Gates will also be faced with a Democrat-controlled Congress after the party’s decisive victory in the midterm elections on November 7, with most in the party demanding an exit strategy.

Senator John McCain, a Republican with ambitions for the White House in 2008 — and also one of the few US politicians advocating more troops in Iraq — asked Mr Gates whether there were too few troops at the outset of the war in 2003.

“Clearly [there] were insufficient troops in Iraq after the initial invasion to establish control over the country,” Mr Gates replied.

Pressed by Mr McCain, Mr Gates said that he was open to the possibility of more troops. But he emphasised that “all options were on the table”, and seemed to indicate a policy that would see a significant reduction in troops.

“It seems to me that the United States is going to have some kind of presence in Iraq for a long time . . . but it could be with a dramatically smaller number of US forces than are there today,” he said.

On Iran, Mr Gates said the US should only attack as “an absolute last resort”, and ruled out any idea of a military strike against Syria.

Different takes

‘Death has a tendency to encourage a depressing view of war’

- Donald Rumsfeld

‘Twelve graduates of Texas A&M have been killed in Iraq. This is very personal for all of us’

- Robert Gates, President of Texas A&M University

‘I don’t do quagmires’

- Donald Rumsfeld

‘The US is going to have some presence in Iraq for a long time’

- Robert Gates

Times Recommends

• A doctor, a daughter and a man called Johnny
• Mona Lisa's smile may have belied ill health
• ‘Parasite economy’ lies behind Greek tragedy