Defense Secretary Robert Gates on Saturday vowed the US military would maintain a "robust" presence across Asia backed up with new high-tech weaponry to protect allies and safeguard shipping lanes.
Seeking to reassure Asian countries mindful of China's growing power and Washington's fiscal troubles, Gates told a security conference in Singapore that Washington's commitment to the region would not be scaled back.
Instead, the US military would expand its presence by sharing facilities with Australia in the Indian Ocean and deploying new littoral combat ships (LCS) to Singapore, where it has regular access to naval facilities, he said.
The LCS is a speedy, lighter ship designed to operate in shallow coastal waters. The waters around Singapore, a staunch US ally, are among the world's busiest commercial sealanes.
Gates said the United States was also considering "prepositioning" supplies to improve disaster response in the region, which has been hit by massive natural disasters like March's killer quake and tsunami in Japan.
Gates, who steps down at the end of the month after more than four years in office, said the US military will conduct more port calls and training programmes with Asian countries as part of its security commitment.
The speech came as countries facing a rising China watch the United States for signs of its long-term security plans in Asia, amid mounting disputes over territorial rights in the potentially resource-rich South China Sea.
Gates called for freedom of navigation, unimpeded economic development and commerce and respect for international law in the region.
He warned that clashes may erupt in the South China Sea unless nations with conflicting territorial claims adopt a mechanism to settle disputes peacefully.
"I fear that without rules of the road, without agreed approaches to deal with these problems, that there will be clashes. I think that serves nobody's interests," he said.
On the US presence in Asia, Gates cited investments in radar-evading aircraft, surveillance drones, warships and space and cyber weapons as proof that Washington was "putting our money where our mouth is with respect to this part of the world -- and will continue to do so".
The planned weapons programmes represented "capabilities most relevant to preserving the security, sovereignty, and freedom of our allies and partners in the region", he said.
They also include maintaining America's nuclear "deterrence" amid continuing concern over North Korea's atomic weapons.
Senior US officials have long pointed to China's military buildup, saying Beijing's pursuit of anti-ship and anti-aircraft missiles as well as cyber warfare capabilities pose a potential threat to US naval power in the region.
Without naming China, Gates said the new hardware was a response to "the prospect that new and disruptive technologies and weapons could be employed to deny US forces access to key sea routes and lines of communications".
Although the Pentagon's budget would come under growing scrutiny and military spending in some areas would be cut back, Gates predicted that investments in the key "modernisation" programmes would be left untouched.
This would ensure "that we will continue to meet our commitments as a 21st century Asia-Pacific nation -- with appropriate forces, posture, and presence", he said.
Gates held talks with his Chinese counterpart Liang Guanglie on Friday on the sidelines of the Singapore meeting.
He said efforts to promote a security dialogue with Beijing had borne fruit and military relations had steadily improved in recent months.