The United States will remain a Pacific power, vice president Joe Biden vowed on Saturday as he credited his country with maintaining peace and stability in the region for decades.
Biden, ending a two-day visit to Singapore, said the US presence there has allowed Asia-Pacific nations to focus on growing their economies.
"I state without apology that we are a Pacific power. America is a Pacific resident power and we will remain so," President Barack Obama's number two told sailors of the US Navy ship USS Freedom.
"The truth of the matter is our resident power status is the reason why this area of the world is able to grow and be stable," he said.
"Our mere presence in the Pacific is in and of itself the basis upon which stability of the region is built. You are the glue that holds all this together."
The USS Freedom is the fastest warship in the US navy – capable of speeds of over 40 knots – and is designed to fight close to shore in areas typical of Southeast Asia's maritime geographical features.
It was in Singapore having completed annual exercises with other Southeast Asian navies. The ship is seen as a symbol of Washington's strategic re-balance of its military presence towards Asia following long wars in Afghanistan and Iraq.
In another speech at a facility of US aerospace giant Pratt & Whitney, Biden said, "the increase in maritime incidents and assertive action which we see lately in the South China Sea represents a threat to the security of the region".
He did not mention any country but Vietnam and US treaty ally, the Philippines, have accused China of mounting aggressive actions in the sea.
Brunei, Malaysia, the Philippines and Vietnam have laid partial claims to the sea, which hosts vital commercial and strategic shipping lanes. Taiwan is the other claimant.
China seized the Scarborough Shoal, a South China Sea outcrop just 230 kilometres (140 miles) east of the main Philippine island of Luzon, last year after Manila backed down from a lengthy stand-off.
This year Manila has complained about the presence of Chinese navy vessels near Second Thomas Shoal, which is occupied by Filipino troops.
Biden on Saturday warned that the risk of a miscalculation in the sea is real and urged claimants to hasten talks on legally-binding rules to prevent conflict.
"It would not take much of an incident to escalate, and tensions can turn into conflict," he said.