GENEVA (AFP) - Australia's programme to equip its navy with nuclear-powered submarines does not fall foul of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), a senior US official insisted on Thursday (Dec 16).

The new defence alliance that Australia officially entered into with Britain and the United States last month could allow it to become the only non-nuclear weapons power to own nuclear-run submarines.

Brazil is also pursuing nuclear propulsion for one of its submarines.

The so-called Aukus deal has faced concerns that it could present a nuclear proliferation risk, with China in particular labelling it an "extremely irresponsible" threat to stability in the region.

But a senior US State Department official, who asked not to be named, insisted on Thursday there was nothing in the NPT, which bars non-nuclear-weapon states from acquiring such weapons, "that forbids that programme that Australia is seeking to conclude with the US and the UK".

The official said Aukus would instead set "a precedent of the highest possible level of safeguards" for any similar deals in the future.

"The world can be absolutely certain that there is no diversion of uranium to a weapons programme," the official said, pointing out that Australia planned to equip the submarines with conventional rather than nuclear weapons, and that it had made clear it would "not build nuclear facilities on its territory that would contribute to a weapons capability".

But such assurances would likely not dissuade China from making an issue of the deal during the next NPT review conference, set to take place in New York next month, the official said.

"I do expect China to raise the question of Aukus every hour on the hour... no matter what the topic of discussion," the official said, suggesting Beijing would use the topic to avoid discussing its own swelling nuclear arsenal.

A report from the Pentagon warned last month that Beijing was on track to more than double its nuclear arsenal to over 1,000 warheads by 2030.

Beijing accused the Pentagon report of "prejudice" and hyping the nuclear threat posed by China.

The State Department official said on Thursday it was unlikely the question of Aukus would prove "an obstacle to achieving a positive outcome" at the NPT review conference - the first since 2015.