The United States is incapable of holding negotiations and it is joining forces with its allies to push Kiev to move against Russia and its territories in an attempt to defeat Moscow, Russian Deputy Foreign Minister Sergey Ryabkov said on Friday.

"The US is not capable of negotiating in general and is pushing Kiev together with London and other NATO countries to move hostilities to our territory, trying to fight until the last Ukrainian to inflict what they call a 'strategic defeat' on Russia," Ryabkov added during a press conference in Moscow.

"Nuclear blackmail has also begun to be used," the senior Russian diplomat noted amid fears on both sides of a nuclear escalation.

Ryabkov said the US deliberately lowered the nuclear threshold, thus, posing threat to Russia's nuclear security.

The Russian diplomat stressed that while his country made no threats against anyone with nuclear weapons, it still warned against the risk of interfering with its goals in Ukraine.

Russian President Vladimir Putin had also accused the west of using the threat of nuclear weapons to blackmail Russia and warned that Moscow will use all means in case its territorial integrity is threatened.

Putin's words prompted US National Security Coordinator John Kirby to say his country took the Russian President's words about nuclear weapons use seriously, though he stressed that Washington saw no need to boost the readiness of its own strategic deterrent forces in the meantime.

Referring to NATO expansion toward Russia's borders, Putin said the West was making schemes to destroy Russia, engaging in "nuclear blackmail" by bringing up the potential use of nuclear weapons against Moscow, and accused the United States, the European Union, and Britain of encouraging Ukraine to push military operations into Russia itself.

Russian Foreign Minister Sergey Lavrov said Thursday that Western countries were becoming a party to the Ukraine war by sending weapons to Kiev with the aim of prolonging the war by as much as possible.

The top Russian diplomat also highlighted that the West's policy meant that its involvement in the conflict made them a party to the war.

Where are Russia and the US on nuclear war?

The Russian ambassador to the United States, Anatoly Antonov, said Friday he wanted to believe his country and the United States were not yet on the verge of nuclear war despite there being many difficulties in their relations.

"With each day, that little, which still glimmers in contacts between the two countries, is fading away. I want to believe that despite all the difficulties, Americans and we are yet to be on the verge of a nuclear conflict," Antonov added.

Russia is still committed to the principle that there is no winner in the nuclear war so it should never be instigated, the ambassador stressed.

"In its aggressive anti-Russian policy, the West has crossed every line," the Russian President said Wednesday. "This is not a bluff. And those who try to blackmail us with nuclear weapons should know that the weathervane can turn and point towards them," he stressed.