Contradicting his Secretary of State and other top officials, US President Donald Trump has suggested that China — not Russia — may be behind what has been called the worst-ever cyber espionage attack on the US Government.

In his first comments on the breach, Mr Trump also downplayed its seriousness and impact.

“The Cyber Hack is far greater in the Fake News Media than in actuality,” Mr Trump said on Twitter on Saturday (local time).

“Russia, Russia, Russia is the priority chant when anything happens because Lamestream is, for mostly financial reasons, petrified of discussing the possibility that it may be China (it may!).”

Mr Trump’s assertion that China may be behind the hacking spree, which has so far affected more than a half dozen federal agencies including the Commerce and

Treasury Departments, runs counter to comments by his own Secretary of State and multiple politicians briefed on the matter.

“We can say pretty clearly that it was the Russians that engaged in this activity,” Secretary of State Mike Pompeo said on Friday in an interview.

In a tweet on Thursday, Republican Mitt Romney said the hack was “like Russian bombers have been repeatedly flying undetected over our entire country”.

The Kremlin has denied any involvement.

The hack targeted software made by US firm SolarWinds and had been going on for months before it was detected last week.

Among the US agencies targeted was the office that manages nuclear weapons, but government officials said the arsenal’s security had not been compromised.

A State Department spokesperson did not immediately respond to a request for comment on Saturday.

Adam Schiff, the Democratic chairman of the House Intelligence Committee, called Mr Trump’s comments a “scandalous betrayal of our national security”.

Another day, another scandalous betrayal of our national security by this president.

Another dishonest tweet that sounds like it could have been written in the Kremlin.

Another obsequious display towards Putin.

And yet another reason that Trump can’t leave office fast enough. https://t.co/ILNh3KnfbT

— Adam Schiff (@RepAdamSchiff) December 19, 2020

In his tweet, Mr Trump tagged Mr Pompeo and Director of National Intelligence John Ratcliffe.

The Office of the Director of National Intelligence, or ODNI, has yet to publicly comment on who is behind the massive data breach, which exploited a piece of software developed by network management firm SolarWinds that is widely used throughout the public and private sectors.

ODNI and the White House’s National Security Council did not respond to a request for comment.

The Kremlin has denied any involvement in the cyber breach.(AP: Patrick Semansky)

Daniel Hoffman, a former CIA Moscow station chief, said the Trump administration needed to quickly explain why Mr Pompeo blamed Russia, while the President cast doubt on that assessment.

Hackers roamed far and wide through the most sensitive security networks. Photo: Getty

Mr Hoffman said that “based on everything we know”, the hack was directed by Russia’s external intelligence service, known as the SVR, using APT29, the Russian hacking group known as Cozy Bear.

He noted that Mr Pompeo served as CIA director before becoming the top US diplomat, and he has “an extremely sophisticated understanding of national security”.

“How is it that he attributed the attack to Russia and the President did not?” he asked.

“We don’t want to speculate that it’s somebody else. We have to be clear in attributing because when you take action in response, you need to be right,” Mr Hoffman said.

– ABC/wires