Two of Donald Trump's top security advisers have paid a rare visit to the Pacific in another sign that the United States is intent on thwarting China's strategic ambitions in the region.

Key points: Experts say Washington has recognised the "new strategic reality" in the Pacific

Experts say Washington has recognised the "new strategic reality" in the Pacific White House recently restructured the NSC to create a new Pacific role

White House recently restructured the NSC to create a new Pacific role The US signed new infrastructure partnerships designed to offer Pacific countries an alternative to China

The senior director for Asian affairs on the White House National Security Council (NSC), Matt Pottinger, visited Vanuatu and Solomon Islands last week for meetings with top politicians and officials. Mr Pottinger also visited Australia, New Zealand and Japan.

He was accompanied by Alexander Gray, who has just taken on a newly created position of director for Oceania & Indo-Pacific Security at the NSC — another sign of intensifying US focus in the region.

The NSC advises US presidents on defence and foreign affairs and has been at the heart of American security policy since World War II.

Ashley Townshend from the United States Studies Centre at Sydney University said Mr Pottinger's visit showed Washington recognised the "new strategic reality" in the Pacific.

"It hasn't been common for the most senior US officials to spend time in the Pacific in past decades. For a range of reasons it hasn't been a top priority," Mr Townshend said.

"But now governments are rediscovering the central strategic importance of the Pacific."

'Greater degree of prioritisation and focus'

Mr Townshend said China's growing presence and influence in the region — as well as the increasing threat posed by illegal fishing and transnational crime — had concentrated minds in Washington.

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And he said it was significant that the White House had decided to restructure the NSC to create Mr Gray's position.

"There has never been a dedicated office in the NSC for the Pacific [before now] — it's been bundled together with other critical parts of the region which have taken more of the bandwidth," Mr Townshend said.

"So you see a much greater degree of prioritisation and focus than you've previously seen. This provides a crucial node."

Australia has also elevated the Pacific within the bureaucracy, establishing an Office of the Pacific with the Department of Foreign Affairs and Trade to coordinate policy across a range of departments.

"With this new office in Australia and this new office in the NSC in Washington you have the institutional start point for much more effective alliance coordination in the Pacific region," Mr Townshend said.

Both the United States and Australia have been wary about the rapid influx of Chinese capital into the Pacific over the last decade and have made a series of high-profile commitments to reassert their influence in the region.

The Trump Administration has pledged to work with Australia and Papua New Guinea to redevelop the Lombrum Naval Base at Manus Island, fuelling speculation it could be used by US Navy ships in the future.

Washington has joined an ambitious project by the governments of New Zealand, Japan and Australia to bring electricity to more than 70 per cent of Papua New Guinea.

It has also signed up to new infrastructure partnerships designed to offer Pacific countries an alternative to China when looking for capital to fund major infrastructure.

The US pledged to work with Australia and Papua New Guinea to redevelop the Lombrum Naval Base. ( Commonwealth of Australia, Department of Defence: Sgt W. Guthrie )

China's influence in the Pacific

Last year US Vice-President Mike Pence used a speech at the APEC summit in Port Moresby to issue a thinly veiled attack on Chinese aid projects in the Pacific.

"Some are offering infrastructure loans to governments across the Indo-Pacific and the wider world, yet the terms of those loans are often opaque at best," he said.

"The projects they support are often unsustainable and poor quality. Too often they come with strings attached and lead to staggering debt."

Chinese naval forces maintain a substantial presence in the contested South China Sea. ( Reuters: China Daily )

The NSC has not commented on the visit, but a US Government source said it "exemplified the importance the United States place on being a strong partner to our friends and allies in the region."

"We are committed to working together with Australia on our shared vision of a free, open, and inclusive Indo-Pacific region that benefits all willing to play fair and follow the rules," the source said.

Pacific nations have welcomed the intensifying US engagement in the region, but they have also warned they do not want to be drawn into a broader strategic battle between China and other powers like America, Australia and France.

Last week the Deputy Secretary General of the Pacific Islands Forum, Cristelle Pratt, criticised the Trump Administration's 2017 National Security Strategy, which says the US will work with Australia and New Zealand to "shore up fragile partner states" in the Pacific and "reduce their vulnerability to economic fluctuations and natural disasters".

Pacific leaders have also insisted they can juggle relationships with both Washington and Beijing. ( Reuters/US Navy: Mass Communication Specialist 3rd Class Adam K. Thomas )

"This narrative continues to paint the picture of a region that is willing to stand by and allow its future to be shaped and directed by others. I would like to encourage you to move away from this narrative," Cristelle Pratt said.

"Of course, Pacific Islands countries face challenges. But we are not fragile and we are not failing."

Several Pacific leaders have also insisted they can juggle relationships with both Washington and Beijing, and have urged both powers to respect their strategic autonomy.