US Defense Secretary James Mattis has said competition between great powers, not terrorism, is now the main focus of America’s national security.
The US faced “growing threats from revisionist powers as different as China and Russia”, he said, unveiling the national defence strategy.
In an apparent reference to Russia, he warned against “threaten[ing] America’s experiment in democracy”.
“If you challenge us, it will be your longest and worst day,” he warned.
America has been gripped by ongoing investigations into alleged collusion between the Trump 2016 election campaign and Russia.
Speaking at John Hopkins University in Baltimore. Mr Mattis also appealed to Congress to fund the military adequately and refrain from “indiscriminate and automatic cuts” to the US federal budget.