Mr Pence said the US was also forging “new and renewed security partnerships”, including recent trilateral naval exercises with India and Japan.

In a strongly-worded speech that took a veiled swipe at China’s strategic creep into the Pacific, Mr Pence also warned developing nations to be wary of accepting large infrastructure loans – increasingly used by China to increase its presence in the region – saying the terms of the deals were “often opaque at best”.

“Projects they support are often unsustainable and poor quality. Do not accept foreign debt that could compromise your sovereignty,” he said.

“Protect your interests, preserve your independence and just like America, always put your country first.”

Mr Pence’s announcement comes as Australia seeks to balance its allegiances to both China and the US.

Speaking to reporters on the sidelines of the APEC summit on Saturday, Mr Morrison, who is due to meet with Mr Pence in Port Moresby, said both allies were equally important.

As Fairfax Media reported in April, China has approached Vanuatu about building a permanent military presence in the South Pacific.

Such a base would allow China to exert military power into the region, and may increase the risk of confrontation between China and the US.

Defence Minister Christopher Pyne last month said the Lobrum upgrades will support the safe and secure berthing of PNG’s four new Guardian-class patrol boats. It builds on existing security cooperation between Australian and PNG defence forces, including a recently established $2 million communications centre at Lombrum.

At the time Labor’s Defence spokesman Richard Marles supported the move, saying “the more cooperation we have with the Pacific, with countries like Papua New Guinea, and that includes military cooperation, I think the better.”

Mr Pence’s announcement fuels an already tense bilateral relationship between the US and China, including the threat of a full-blown trade war. The US imposed tariffs on $200 billion of Chinese imports in September and has threatened to extend this to almost all of China's exports to the US.

China retaliated by saying it would impose duties on $60 billion worth of US goods.

In an earlier speech, Prime Minister Scott Morrison mounted a spirited defence of the benefits of free trade, saying “tit-for-tat protectionism and threats of trade wars are in no-one’s interests economically and undermine the authority of the global and regional trading rules that benefit us all”.

The federal government has been contacted for comment on the Manus announcement.