A more assertive China poses a «systemic challenge» to the global order, UK Prime Minister Rishi Sunak told NBC News on Sunday, as Britain, the United States and Australia planned to unveil the latest steps in a defense partnership. to counter Beijing’s growing military might.

«The behavior that we’ve seen in China of late is concerning,» Sunak told NBC News’ Lester Holt at the USS Midway Museum shortly after arriving in San Diego for the three-way summit. China is «acting in a more authoritarian way at home» and is «more assertive abroad,» he said.

Catch more of the interview Monday on “NBC Nightly News with Lester Holt” at 6:30 pm ET/5:30 pm CT.

“China represents the biggest state threat to our economic interests, without a doubt. And it is a systemic challenge to the world order,” Sunak said.

President Joe Biden will host Sunak and Australian Prime Minister Anthony Albanese in San Diego to endorse newly agreed initiatives for the AUKUS defense pact, 18 months after the partnership was announced. The ambitious defense partnership aims to deliver nuclear-powered submarines to Canberra as part of a bid to counter China’s military buildup in Asia.

Lester Holt interviews Sunak aboard the USS Midway Museum in San Diego on Sunday.Jim Seida/NBC News

China responded by calling the AUKUS submarine deal «a flagrant act of nuclear proliferation» that undermines regional peace and stability.

Sunak, a former billionaire banker and finance minister, also weighed in on the collapse of Silicon Valley Bank after federal regulators stepped in to support the lender’s deposits, saying it was important to a host of British tech companies.

“I have been working over the weekend with our finance minister, the chancellor and our Bank of England, our regulators, to find a suitable solution. We will make an announcement about it very soon,” he said.

Sunak, 42, took office on October 25 after a period of political turmoil, becoming the UK’s third leader in seven weeks following the collapse of Boris Johnson’s scandal-plagued government and implosion at the speed of the light by Liz Truss.

He cited a summit with French President Emmanuel Macron in France last week and the trilateral meeting scheduled for Monday in San Diego as examples of Britain playing a vital role on the world stage.

«Britain is back,» he added.

Pending congressional approval, Australia is expected to acquire up to five Virginia-class nuclear-powered submarines from the US in the 2030s under the AUKUS deal, while Britain and the US plan to help Australia to build its own nuclear powered fleet.

While citing concerns about his actions, Sunak said there is still a place for engagement with China, including on climate issues and the stability of the global economy.

Asked how Britain would respond if China tried to seize Taiwan through military force, Sunak declined to answer directly.

Taiwan, an autonomous island that Beijing claims as its territory, is under increasing pressure from China, which has not ruled out using force to seize control of the island. Taiwan’s most important international backer is the United States, which is required by law to provide it with defensive weapons, but has long been vague about whether it would intervene militarily if the Chinese attacked.

Sunak said the international response to Russia’s invasion of Ukraine served to deter any country from launching an unprovoked attack.

“I think the best thing we can do to deter hostile action by any state anywhere is to do what we’re doing right now in Ukraine. And that is where we have seen an unprovoked and illegal invasion of Ukraine by Russia. And the right thing to do in that circumstance is to give Ukraine all the support it needs to defend itself,” he said.

On Western military aid to Ukraine, he said: «I think it is important at this time that we accelerate and intensify our support for Ukraine.»

He said London’s commitment to the AUKUS defense pact was part of a general increase in defense spending by Britain, which he said would remain a leading military power. The British government announced plans on Sunday to increase its defense spending by nearly $6 billion over the next two years.