US Defence Secretary Leon Panetta has embarked on a nine-day trip to Asia which will include what a senior defence official calls a "major policy speech" about the US role in the Asia-Pacific region.

With US troops out of Iraq and soon to draw down from Afghanistan, the Obama administration is putting an increased focus on the Asia-Pacific region, calling it a rebalance of foreign policy and defence priorities.

When the country's new Defence Strategic Guidance was issued in January, Panetta said: "The US military will increase its institutional weight and focus on enhanced presence, power projection, and deterrence in Asia-Pacific. 

"This region is growing in importance to the future of the United States in terms of our economy and our national security."

On this trip, Panetta will make stops in Singapore, Vietnam, and India.

"The core of what we're trying to do with this swing through Asia is give a comprehensive account to partners and everyone in the region about what the rebalance to the Asia-Pacific will mean in practice," said a senior defence official.

Panetta will deliver the major policy speech at the Asia Security Summit, or Shangri-La Dialogue, in Singapore on Saturday.

In the past six months, the US deployed a contingent of Marines to Australia and announced a realignment of US bases in the region. 

Some analysts say the rebalance is meant to counter China's growing power in the region. When the deployment of Marines was announced last November, Chinese Foreign Ministry spokesman Liu Weimin said: "It may not be quite appropriate to intensify and expand military alliances and may not be in the interest of countries within this region." 

US officials deny the rebalance is in response to any one country. But defence officials won't confirm if Panetta will meet his Chinese counterpart during the trip.

As members of Congress consider cuts to defence spending, Panetta will use the speech to address how the rebalance will be resourced. 

Senior defence officials say Panetta will also clarify what the rebalance means for the US's military posture in the Asia-Pacific region.

Follow Camille Elhassani on Twitter: @celhassani