"So far so good," General George Casey, the top US commander in Iraq told reporters Friday at Tallil Air Base in southern Iraq after a lightning tour of military installations in Basra and Tallil with Gates.

In an intense weeklong trip, Gates road tested his ideas for strengthening a badly weakened US position in Iraq and the region, placing a clear emphasis on flexing US military and diplomatic muscle despite the strains of a long war.

He met with NATO allies in Europe, endorsed commanders requests for more US troops in Afghanistan, and conferred with rulers of Saudi Arabia and the Gulf on his concerns that regional rival Iran is riding high on US difficulties in Iraq.

"Whatever one's views on how we got to this point here in Iraq, at this pivotal moment there is widespread agreement that failure would be a calamity for America's national interests and those of many other countries," Gates said as he ended the trip.

Striking a contrast with his predecessor Donald Rumsfeld who relished setting a brutal pace for himself and his entourage, Gates, a self deprecating former CIA director, quipped that he had learned at least one fact.

"I'm too old to do seven countries in five and a half days."

With only one month on the job, Gates said he was looking for "ground truth" on the situation in Iraq and Afghanistan and the larger Gulf region.

Polite skepticism appeared to be the reaction from allies and other friendly countries who wished him well but offered no tangible commitments to the new policy.

In London, the United States' closest ally in the Iraq war told Gates they planned to proceed with the withdrawal in the coming months of several thousand troops from Iraq, a good chunk of 7,000-strong British contingent.

The United States is sending an additional 20,000 US troops to try to put out the sectarian fire in Baghdad, but the British said the situation in the predominantly Shiite south is quieter and therefore different.

In Riyadh, Saudi King Abudullah listened to Gates' pitch for more reconstruction and development aid for Iraq but made no commitments and expressed nervousness about the Maliki government, US officials said.

During Gates' visit to Qatar, the site of the regional headquarters of the US Central Command and a huge air base used by the US air force, reporters were kept at an air base "somewhere in Southwest Asia" while the secretary met with the emir.

Because of the host nation's sensitivities, reporters traveling with Gates were required to sign secrecy agreements forbidding them from saying what base in what country Gates flew to for the Qatar leg of his trip.

In the Gulf, Gates' theme was deepening US concern over Iranian expansion.

Just two years ago, he said, Iran was playing a more constructive role in Iraq and Afghanistan. With US forces on their eastern and southern borders the Iranians weren't sure what would come next, he said.

Now, he said, the Iranians "believe they have the United States at some disadvantage because of the situation in Iraq."

"We need some leverage, it seems to me, before we engage with the Iranians," he told reporters during a stop in Bahrain.

"I think until the Iranians have some sense that the United States is in fact a formidable adversary, that there's not much advantage for us for engagement."

The United States is sending a second aircraft carrier battle group to the Gulf region as well as Patriot missile defense batteries, building the US military's presence in the Gulf to its highest level since the US invasion of Iraq in 2003.

However, no major change in the posture of Iranian naval forces in the Gulf has been detected over the past year, said Commodore Keith Winstanley, deputy commander of a combined coalition maritime force based in Bahrain, raising questions about what the second carrier will do.

Work on a "concept of operations" for the USS John C Stennis has not finished yet, Winstanley said.

Iranian activities in Iraq have also remained elusive.

In Basra, British army Major Chris Ormond told reporters Iranian agents are suspected of hiring "rogue elements" of Shiite militias to attack coalition forces, but no hard evidence has been found that it is smuggling in advanced weaponry for the attacks.

US forces, however, have detained Iranians in at least two recent raids in their sectors targeting individuals allegedly linked to attacks on coalition forces.

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