SINGAPORE (Reuters) - As many in Asia question the durability of the United States’ long-standing security role in the region, one veteran military commander is reassuring old allies and newer friends that nothing has changed.

FILE PHOTO: The Commander of the U.S. Pacific Command, Admiral Harry Harris, testifies before a House Armed Services Committee hearing on "Military Assessment of the Security Challenges in the Indo-Asia-Pacific Region" on Capitol Hill in Washington, U.S, April 26, 2017. REUTERS/Yuri Gripas/File Photo

Admiral Harry Harris, commander of the U.S. Pacific Command (PACOM), has emerged as the frontman of Washington’s strategic diplomacy in Asia, according to several military officials, diplomats and analysts.

From his base in Hawaii, the 60-year-old former PC-3 maritime patrol pilot has spent the last two years shuttling constantly across the region, grappling with issues like North Korea, the disputed South China Sea and the spread of jihadist movements.

But Harris has a tougher task as he serves a new administration - he has to shore up U.S. alliances amid growing worries in the region that Washington’s pullout from the Trans-Pacific Partnership (TPP) trade pact and the Paris climate accord signals a withdrawal from a global role.

Asian nations worry that any diluted U.S. presence, just a few years after former president Barack Obama’s strategic rebalance to the region, could leave them at the mercy of an increasingly assertive China.

Carl Thayer, a regional security analyst at the Australian Defense Force Academy, said the U.S. Pacific commander is like a pro-consul of old, with vast delegated authority and responsibility across 36 nations. He knows both political leaders and senior military officials personally.

“But at this moment, he’s something more - he’s the very glue holding the traditional U.S. line together across Asia,” Thayer said.

As one of America’s six combatant commanders, Harris reports to President Donald Trump through the Secretary of Defense. But the Pacific command is by far the biggest of the U.S. military commands - it accounts for 60 per cent of all U.S. navy ships, 55 per cent of army forces and two-thirds of its fleet marine forces. It will soon account for 60 percent of U.S. tactical aviation assets overseas.

At the annual Shangri-La Dialogue security gathering in Singapore last weekend, Harris operated behind closed doors as U.S. Defense Secretary Jim Mattis pushed China to rein in North Korea and end its militarization in the South China Sea.

U.S. officials said Mattis’s speech at the forum reflected Harris’ firm views on the need to stand up to China. It also addressed the fears of Asian allies that Washington was willing to give China a more free role in the region in exchange for tackling North Korea.

Harris has described U.S. challenges as including “an aggressive China and a revanchist Russia.”

In a statement to Reuters this week, he said: “We will continue to co-operate where we can, but have to be ready to confront if we must.”

“So I simply continue to focus on building critical relationships while ensuring that we have credible combat power to back up our security commitments and to help American diplomacy operate from a position of strength.”

America’s alliances, he added, were “ironclad”.

CHINA BRISTLES

Harris’ statement came from Australia, a long-standing ally he is visiting with Mattis and Secretary of State Rex Tillerson.

It is one of 10 country visits he’s made since Trump was elected - missions that have included nations as diverse as Japan, Sri Lanka and Papua New Guinea.

Chinese officials openly bristle at some of Harris’ remarks, and the state press has criticized his explicit backing of Beijing’s long-time rival Japan, with some reports noting his Japanese heritage. Harris was born in Yokosuka to a Japanese mother and American father serving with the U.S. navy.

The Chinese Foreign Ministry denied, however, a Japanese press report last month that a senior Chinese envoy had demanded the Trump administration fire Harris.

Those who have served with Harris insist he is well equipped to deal with the pressures he faces, while some of his foreign military peers respect him as a straight shooter.

“He is brusque and is a demanding boss, but he inspires loyalty from those who make it, and shows great loyalty as well,” said one former staffer.

Some U.S. officials acknowledge that Harris is playing a greater role to reassure allies, in part because a number of senior positions have not been filled by the Trump administration in the Pentagon and State Department. They expect once those positions are filled, he will share less of a burden in reassuring allies.

As the pressures mount five months into the Trump presidency, some note that Harris nonetheless faces an uphill battle to ease fears in the region.

“In the face of “America First,” withdrawal from TPP and the Paris climate accord, the region is looking for a lot more reassurance than Commander Harris can provide,” said Bonnie Glaser, a regional security expert at the Center for Strategic and International Studies in Washington.

(This story fixes typo in para 21.)