The Kremlin said on Monday that everyone should be careful about nuclear rhetoric, in its first response to a statement by U.S. President Donald Trump that he had ordered a repositioning of U.S. nuclear submarines.

Kremlin spokesman Dmitry Peskov played down the significance of Trump's announcement last Friday that he had ordered two subs to be moved to "the appropriate regions" in response to remarks from former Russian president Dmitry Medvedev about the risk of war between the nuclear-armed adversaries.

"In this case, it is obvious that American submarines are already on combat duty. This is an ongoing process, that’s the first thing," Peskov told reporters.

"But in general, of course, we would not want to get involved in such a controversy and would not want to comment on it in any way," he added. "Of course, we believe that everyone should be very, very careful with nuclear rhetoric."

Peskov said that Russia did not see Trump's statement as marking an escalation in nuclear tension.

"We do not believe that we are talking about any escalation now. It is clear that very complex, very sensitive issues are being discussed, which, of course, are perceived very emotionally by many people," he said.

Peskov declined to answer directly when asked whether the Kremlin had tried to warn Medvedev to tone down his online altercation with Trump.

"Listen, in every country, members of the leadership... have different points of view on events that are taking place, different attitudes. There are people who are very, very tough-minded in the United States of America and in European countries, so this is always the case," he said.

"But the main thing, of course, is the position of President (Vladimir) Putin," he said. "You know that in our country, foreign policy is formulated by the head of state, that is, President Putin."