US will act to protect if China threatens its sovereignty, says Biden

Amidst growing tension with China over a suspected surveillance balloon, US President Joe Biden has said that the United States will act to protect if Beijing threatens its sovereignty.

"I am committed to work with China where it can advance American interests and benefit the world. But make no mistake: as we made clear last week, if China threatens our sovereignty, we will act to protect our country. And we did," Biden said in his State of the Union Address on Tuesday night.

The US military downed the suspected Chinese spy balloon over the Atlantic Ocean last week, drawing a strong reaction from China which on Sunday warned of repercussions over America's use of force against its civilian unmanned airship.

The US has accused China of violating American sovereignty and international law.

"Let's be clear: winning the competition with China should unite all of us. We face serious challenges across the world. But in the past two years, democracies have become stronger, not weaker, he said in his second State of the Union Address before a Joint Session of the US Congress.

In his speech, which revolved around the theme of unity, Biden said two years into his administration, autocracies have grown weaker, not stronger.

"America is rallying the world again to meet those challenges, from climate and global health, to food insecurity, to terrorism and territorial aggression, he said in his address three months after Republicans took control of the House of Representatives.

"Allies are stepping up, spending more and doing more. And bridges are forming between partners in the Pacific and those in the Atlantic. And those who bet against America are learning just how wrong they are. It's never a good bet to bet against America, Biden said.

Mentioning China a dozen times in his speech, Biden said before he came to office, the story was about how China was increasing its power and America was falling in the world.

"Not anymore. I've made clear with President Xi (Jinping) that we seek competition, not conflict, Biden said, amidst applause.

"I will make no apologies that we are investing to make America strong. Investing in American innovation, in industries that will define the future, and that China's government is intent on dominating. Investing in our alliances and working with our allies to protect our advanced technologies so they're not used against us," he said.

"Modernising our military to safeguard stability and deter aggression. Today, we're in the strongest position in decades to compete with China or anyone else in the world, he said.