China will not surpass US

US President Joe Biden on Thursday said he would prevent China from passing the United States to become the most powerful country in the world, vowing to invest heavily to ensure America prevails in the rivalry between the world's two largest economies.

Biden said he had spent "hours upon hours" with Xi Jinping when he served as vice president under former President Barack Obama, and was convinced the Chinese president believed autocracy - not democracy - held the key to the future.

The Democratic president said he had made it clear to Xi that the United States was not looking for confrontation, but would insist China abide by international rules for fair competition, fair trade and respect for human rights.

"China has an overall goal ... to become the leading country in the world, the wealthiest country in the world, and the most powerful country in the world," he told reporters at the White House. "That's not going to happen on my watch because the United States is going to continue to grow."

Biden took aim at Xi and Russian President Vladimir Putin for embracing autocracy.

"He's one of the guys, like Putin, who thinks that autocracy is the wave of the future, (and) democracy can't function in an ever-complex world," the president told his first news conference since taking office in January.

Earlier in March, Biden told ABC News he believed Putin was "a killer," which sparked fury in Moscow, reports Reuters.

"He (Xi) doesn't have a democratic - with a small 'd' - bone in his body, but he's a smart, smart guy," he said.

The US president also warned North Korea that the United States will "respond accordingly" if it escalates its military testing, after Pyongyang fired two missiles in its first major provocation since he took office.

The nuclear-armed North has a long history of using weapons tests to ramp up tensions, in a carefully calibrated process to try to forward its objectives, reports AFP.

Biden's response demonstrates a change of tone from his predecessor Donald Trump, who engaged in an extraordinary diplomatic bromance with North Korean leader Kim Jong Un and last year repeatedly played down similar short-range launches.

Pyongyang had been biding its time since the new administration took office, not even officially acknowledging its existence until last week.