US Secretary of State Hillary Clinton is set to make a rare foray to the South Pacific this week, in a move analysts say is aimed at curbing China's growing influence among the region's small island nations.

While Clinton's previous trips to the area have focused on Canberra and Wellington, this time she is expected to visit the Cook Islands, a nation of just 11,000 people whose 15 islands cover an area barely larger than Washington DC.

The reason is to attend a regional summit hosted by the Pacific Islands Forum (PIF), a group consisting mainly of small island states, along with resource-rich Papua New Guinea and the dominant regional powers Australia and New Zealand, both US allies.

The impoverished, strategically unimportant island states dropped off Washington's radar many years ago, former New Zealand diplomat Michael Powles said, as China cultivated diplomatic ties through aid and bilateral agreements.

Powles, a senior fellow at the Centre for Strategic Studies in Wellington, said the presence of Washington's top diplomat at the PIF summit would send a pointed message to Beijing that the US intends to re-engage in the region.

"If you're going to be crude about it, it's almost the Americans saying 'Hey, don't forget about us'," he told AFP.

"The US has suddenly started doing a lot more in the Pacific after quite a long time of doing the absolute minimal amount, whereas over the last few years China has been pretty active."

Forum organisers have prepared for Clinton's visit, although the US State Department has not confirmed her travel plans, in line with normal protocols.

Annmaree O'Keeffe, a Pacific specialist at Australia-based think-tank the Lowy Institute, said Washington's renewed focus on the island states was part of a broader move in US foreign policy towards the Asia-Pacific region.

The policy involves the US boosting diplomatic and military resources in the Asia-Pacific, now recognised by the US as a key driver in the global economy, while its engagement in Iraq and Afghanistan winds down.

However, some aspects, such as US plans to deploy 2,500 Marines to northern Australia and boost its naval presence in the Pacific, have rankled China, which has increased its military spending in recent years.

O'Keeffe said Clinton's expected appearance at the Cook Islands PIF was "a sideshow" in the larger context of Washington's policy shift but represented the US waving the flag in even the remotest areas of the Pacific.

"When you have a summit like this it brings together all the main players in one spot, so it's an important place to be if you're trying to rebuild your knowledge and influence in the region."

The United States has its own Pacific territories in Guam, the Northern Marianas, Hawaii and American Samoa, as well as close ties with Palau, Micronesia and the Marshall Islands.

However, excluding American Samoa, they are all located in the northern or central Pacific, leaving the South Pacific with scant attention from Washington in recent years.

O'Keeffe's Lowy Institute estimated last year that China had pledged more than US$600 million since 2005 in "soft loans" offering long interest-free periods to nations such as Tonga, Samoa and the Cook Islands.

In contrast, she said the major commitment the US currently has in the South Pacific was a recently-announced US$20 million environmental programme.

Powles said while China may be mildly suspicious about US attempts to improve diplomatic ties in the South Pacific, its chief concern would be if Washington pushed the island nations to agree to more military cooperation.

"It's a question of whether the countries are being asked to be part of the Western (US-led) team and if that would involve regular naval visits and Marines coming, as they're starting do do in northern Australia," he said.

"That would concern the Chinese and be likely to strengthen the people in China who feel they've had enough of the West and the US trying to prevent them emerging as a major power -- that could lead to explosive consequences."