US military shows off nuclear capable submarine in Western Australia

The United States military is flexing its nuclear fleet of submarines in Western Australia.

The arrival of the USS North Carolina is the first visit since a landmark defence deal was signed earlier this year.

Australia is buying eight of the nuclear-powered Virginia class submarines in a deal costing $368 billion.

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Australia's Ambassador to the US Kevin Rudd was on Garden Island touring the 110-metre vessel which can go three months underwater.

WA will permanently house nuclear subs from next decade.

HMAS Stirling is set for an upgrade as thousands more submariners file through Perth.

It is part of plans to bolster the Indo Pacific against any Chinese naval threat.

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The public is not allowed to know how long the North Carolina will be docked in Perth - that information is classified even from Australia's defence minister.

However, there have been reassurances the AUKUS deal is watertight regardless of who is in the White House.

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Advisor to the US secretary of defence Abe Denmark said there has been broad bipartisan support.

Rudd described the move as an opportunity to step up the capabilities of the Royal Australian Navy and the sovereign capabilities of Australia "in a highly uncertain period strategically".

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