Plans to expand the American naval presence in the Pacific with new ships and hi-tech weaponry will go ahead despite steep budget cuts, the US Navy chief said before a trip to the region.

Admiral Jonathan Greenert told AFP in an interview he will seek to "reassure" partners during a nine-day trip to Japan, Singapore and South Korea that mounting pressure on military spending will not derail Washington's much-publicized shift towards Asia.

Of the navy's current fleet of 283 ships, 101 are deployed and 52 are in Pacific waters, with plans to increase the US presence in the region to 62 ships by 2020, he said.

"We're going to grow. There's no question about the next seven to eight years," said the admiral, who departs Wednesday on his tour.

Greenert, who will meet counterparts at the IMDEX maritime security conference in Singapore, said during his talks he would outline a steadily expanding naval presence, particularly in Southeast Asia.

"I'll talk to them on deployments and how we're going to sustain our presence out there through this 2013-14 period," he said.

Under automatic budget cuts, the Pentagon faces a reduction of $41 billion this fiscal year and possibly up to $500 billion over the next nine years if US lawmakers fail to break a political impasse.

Military leaders have warned that flight hours, ship maintenance and some exercises will be scaled back due to the belt tightening, even as China and other Asian powers pursue an arms buildup.

Greenert acknowledged the cuts could slow down the arrival of some new weapons, and if funding were slashed over several years, ship-building plans would suffer.

But he said there were 47 ships under construction or under contract that would not be affected by any budget slashing.

"Shipyards won't go empty. There's no plan to break the contracts."

For the Pacific, he touted efforts to strengthen the navy's role in the region, from more joint drills to "more grey hulls" in the western Pacific.

The strategic "re-balance" is illustrated by what Greenert calls operating "forward," with 42 of the 52 vessels patrolling the Pacific permanently stationed in regional ports.

The approach paid off amid recent tensions with North Korea, he said, when two US destroyers were ordered to the coast off the Korean peninsula.

The warships were close at hand in Japan at the naval base in Yokosuka, instead of having to travel a vast distance from the US West Coast.

"They are where it matters, when it matters," he said.

The military also plans to send the latest cutting-edge hardware to Asia, with the first squadron of the new P-8 Poseidon aircraft to arrive in Japan later this year, he said.

The new Littoral Combat Ship (LCS) will have a prominent role in the Pacific, he said, which would free up bigger amphibious ships and destroyers for duties elsewhere.

The first LCS, the Freedom, arrived in Singapore last month for its inaugural mission, with four of the ships due to use the port through 2017.

The Pentagon believes the smaller LCS vessels are more compatible with similar-sized ships used by other navies in the region, and more suited to an area plagued by territorial disputes.

Given tensions over territorial rights in the South China Sea and beyond, Greenert said he would use his trip to discuss "protocols" at sea with partners to prevent crises.

"We'll talk about protocols -- how we want to operate together at sea and, when together, how would we operate and conduct ourselves if challenged, say in the South China Sea or East China Sea?" he said.

China is often at odds with its neighbors over territorial rights and a Pentagon report issued Monday accused Beijing of cyber espionage against the US government.

But Greenert said he did not view the Asian power as threat.

Instead, relations with China represented an "opportunity," which if not handled correctly "could turn into a potential adversary."

Washington was focused on how to "understand each other and develop a meaningful dialogue."

The four-star admiral, who travels to Seoul after his stop in Singapore, said North Korea remained the biggest threat in the region, but that tensions had receded after Pyongyang toned down its bellicose language in recent weeks.

North Korea still had the ability to launch missiles but "the likelihood has gone down," he said. "The rhetoric has lowered."