Washington DC - The US will ensure "robust, ready and credible deterrence" across the Taiwan Strait, US Defense Secretary Pete Hegseth said Sunday, calling China "aggressive and coercive."

Hegseth also stopped short of publicly calling on Tokyo to hike military spending, saying in Japan that he trusted the close US ally to "make the correct determination of what capabilities are needed."

"America is committed to sustaining robust, ready, and credible deterrence in the Indo-Pacific, including across the Taiwan Strait," Hegseth said, using Washington's term for the Asia-Pacific region.

Beijing has stepped up military pressure in recent years around Taiwan, including near-daily air incursions, and has not ruled out using force to bring the self-ruled island under its control.

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US President Donald Trump's "America First" approach could mean weakening the US commitment to security in the region, analysts have warned.

But Hegseth said the previous US administration had "created this vacuum, a perception that America was not strong, and wasn't prepared to deter conflicts from starting."

"Our job now at this moment, here with our allies, is to say: We are re-establishing deterrence. Peace through strength, with America in the lead, is back," the Pentagon chief told reporters.

He said Washington would "build an alliance so robust that both the reality and the perception of deterrence is real and ongoing so that the Communist Chinese don't take the aggressive actions that some have contemplated they will."

Hegseth, a former infantryman and Fox News personality, hailed the "extraordinary strength of America's alliance with Japan."

"President Trump has also made it very clear, and we reiterate, we are going to put America first. But America first does not mean America alone," he said.

"America and Japan stand firmly together in the face of aggressive and coercive actions by the Communist Chinese."

There have also been expectations that, as he has done in Europe, Trump would press its allies in Asia to increase military spending and to do more to ensure their own defense.

"We have a great relationship with Japan. But we have an interesting deal with Japan that we have to protect them, but they don't have to protect us," Trump said this month. "I actually ask, who makes these deals?"