Defence secretary Robert Gates plans to reassure anxious allies in Asia this week that the US military will maintain a strong presence in the region despite budget pressures at home, officials said.

The Pentagon chief will address the allies' concerns "head on" at a security conference this week in Singapore, said a senior defence official, who spoke on condition of anonymity.

As Washington moves to tackle a ballooning deficit and debt, Asian allies fear a scaling back of the US military's role just as China's armed forces take a more assertive stance, defence officials said.

"There's no doubt that the region has that concern, and I think it's one that we're well aware of, and hence it's one the secretary will want to address," the official told reporters.

Gates, who departs on Tuesday on his global tour, will seek "to assure the region that we will maintain our commitments in the region and that we have both the capability in addition to the will to do so," the official said.

In a speech in Singapore, Gates is "going to talk in greater detail than in the past about what we in DoD (department of defence) are doing to make that more tangible, specifically in terms of US presence in the region," the official said.

Gates will stress that the United States is "not distracted" from defence issues in Asia despite crises elsewhere in the world, the official said.

In his last international trip as defence secretary before he steps down at the end of June, the speech at the security summit in Singapore will offer a chance for Gates to discuss US policy on Asia and the underlying principles that guide it, officials said.

After arriving on Thursday in Singapore following a stop in Hawaii, Gates plans to meet with his Chinese counterpart, Liang Guanglie, to try "to build on the positive momentum that exists in the military-to-military relationship right now," a second official said.

Last year's conference in Singapore was marked by sharp exchanges between Gates and senior Chinese generals, who said US arms sales to Taiwan remained a serious obstacle to building a security dialogue between the two countries.

But officials have cited positive signs more recently, with Gates having traveled to China in January and the People's Liberation Army Chief of General Staff Chen Bingde making a week-long US visit earlier in May.

During his US tour, Chen struck a mostly conciliatory tone and said his country had no plans to take on the American military in the Pacific.

In his talks with Liang in Singapore, Gates hopes to renew his proposal for a civilian-military dialogue that would address "sensitive security issues," including nuclear weapons, missile defence and cyber warfare, officials said.

The Chinese have yet to agree to the idea.

The United States has also disagreed with Beijing over the South China Sea, saying it has a right to sail US naval ships in the area and backing calls from smaller countries for a diplomatic arrangement to settle territorial disputes.

The Spratlys, a reputedly oil-rich South China Sea island chain, is claimed in whole or in part by China as well as Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

At the Asia security conference, Gates plans to meet his counterparts from Japan, Australia, Thailand and Singapore as well as Malaysia's Prime Minister, officials said.

After Singapore, Gates was due to attend a meeting of Nato defence ministers in Brussels, where the air campaign in Libya and the war in Afghanistan are expected to dominate the agenda.