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President Barack Obama has said in a TV interview that the US is engaging in "tough talk" with China about its alleged cyber attacks on America.

Mr Obama told ABC News some, but not all, hacking originating from China was state sponsored, although he played down congressional talk of a cyber war.

He spoke a day after US intelligence chiefs said cyber attacks had replaced terrorism as the main security threat.

China denies such hacking and says it is the victim of such attacks.

Mr Obama was asked in the interview with ABC News, broadcast on Wednesday, about claims from US lawmakers that the scale of attacks on American firms and infrastructure amounted to a cyber "war" with China.

"You know, there's a big difference between them engaging in cyber espionage or cyber attacks and obviously a hot war," the president said.

"What is absolutely true is that we have seen a steady ramping up of cyber security threats. Some are state sponsored. Some are just sponsored by criminals.

"We've made it very clear to China and some other state actors that, you know, we expect them to follow international norms and abide by international rules.

"And we'll have some pretty tough talk with them. We already have."

China has long been suspected of a role in cyber attacks, prompting Pentagon warnings that America must guard against a "digital Pearl Harbor". A US congressional report last year named China as "the most threatening actor in cyberspace".

The issue has become a growing bone of contention between Washington and Beijing.

On Tuesday, US Director of National Intelligence James Clapper told a Senate committee that cyber attacks and cyber espionage had supplanted terrorism as the top security threat facing the country.

A day earlier in New York, US National Security Advisor Tom Donilon called on Beijing to take steps to stop cyber crime.

Last month, a report from US security firm Mandiant said a unit of China's People's Liberation Army had mounted data raids on the computer systems of more than 140 mostly US-based organisations.

US state department officials have said hacking comes up "in virtually every meeting we have with Chinese officials".

In January, the New York Times said it had been subject to cyber attacks from China, following the newspaper's report on the wealth of outgoing Premier Wen Jiabao's family.