In its new military strategy, the American government sees China as the greatest permanent threat.
It is the only country that "both wants to restructure the international order and increasingly has the strength to do so," said Secretary of Defense Lloyd Austin when presenting the strategy on Thursday.
Russia is classified as an "imminent" threat.
The word was chosen carefully, Austin emphasized.
"Unlike China, Russia cannot systematically challenge the United States in the long term," Austin said.
"But Russian aggression is a direct and acute threat to our interests and values."
With regard to the use of American nuclear weapons, it is said that a very high threshold will continue to be set.
However, the strategy does not stipulate that they should only be used in response to a nuclear attack.
For North Korea, the strategy includes a warning that using nuclear weapons against the US or its partners would mean "the end of the regime" of ruler Kim Jong-un.
"There is no scenario in which Kim's regime could use nuclear weapons and survive," the Pentagon said.
With regard to Iran, it is said that the country does not currently have a nuclear weapon "and we currently believe that it is not trying to get one".
However, Iran is building nuclear capabilities that would allow nuclear weapons to be developed.