Putin said that 150,000 of these were deployed in Ukraine, with 77,000 in combat units and the remainder in defensive roles and the remaining 150,000 people were still in training facilities

Russian President Vladimir Putin has said that the threat of nuclear war is growing, but he has insisted that Moscow has not “gone insane” and will not use its arsenal first.

The US was quick to condemn what it called “loose talk” about nuclear weapons after Putin said Russia would only use nuclear weapons in response to an enemy strike.

“We think any loose talk of nuclear weapons is absolutely irresponsible,” US State Department spokesman Ned Price told reporters.

Following Putin's thinly veiled nuclear threat in September, the US previously warned Moscow about the use of nuclear weapons.

During a televised meeting of his human rights council on Wednesday, Putin said Russians would “defend ourselves with all the means at our disposal.”

The latest in a series of such warnings, he warned that the risk of nuclear war was growing, but that Russia saw its arsenal as a means of retaliation, not of striking first.

“We haven't gone insane, we understand what nuclear weapons are,” Putin said.

“We have more advanced and modern nuclear weapons than any other nuclear country… But we're not going to go around the world wielding this weapon like a razor,” he added.

Putin meets with the council annually, which critics say allows him to pay lip service to civic freedoms while increasing repression and stamping out dissent.

Putin also said that Russian forces could be fighting in Ukraine for a long time, but he sees “no sense” in mobilising more troops at this time.

“As for the duration of the special military operation, of course, this can be a long process,” Putin said of Russia's invasion, which began in late February.

After a call-up of at least 300,000 reservists in September and October, he said there was no need for a second mobilisation.

Putin said that 150,000 of these were deployed in Ukraine, with 77,000 in combat units and the remainder in defensive roles. The remaining 150,000 people were still in training facilities.

“Talking about any additional mobilisation measures simply makes no sense under these conditions,” he said.

Putin has rarely discussed the war's likely duration, despite boasting in July that Russia was just getting started.

Russia has been forced to retreat significantly since then, but Putin has said that he has no regrets about starting the war, Europe's most devastating since World War II.