The warning from Russia’s defence committee deputy chairman, Aleksey Zhuravlyov, comes as Finland is poised to join Nato, and Sweden is set to follow suit.
“If Finland wants to join this bloc, then our goal is absolutely legitimate - to question the existence of this state. This is logical,” Mr Zhuravlyov said in an interview with state TV Russia 1.
“If the United States threatens our state, it’s good: here is the Sarmat for you, and there will be nuclear ashes from you if you think that Russia should not exist. And Finland says that it is at one with the USA. Well, get in line.”
Last month Russia tested its new intercontinental missile, the Sarmat also known as the Satan 2. It announced that the warhead which could target Europe and the US, would be deployed by the autumn.
The Sarmat is capable of carrying 10 or more nuclear warheads and decoys, and of striking targets thousands of miles away.
Asked if Russia would now rebase nuclear weapons onto its border with Finland, he said: “What for? We don't need to.
“We can hit with a Sarmat from Siberia, and even reach the UK. And if we strike from Kaliningrad... the hypersonic's reaching time is 200 seconds - so go ahead, guys.
“On the Finnish border we will have not strategic weapons, but Kinzhal-class, one that will reach Finland in 20 seconds, or even 10 seconds.”
Russia has voiced its discontent at Finland’s intention to join Nato and said it would take “retaliatory steps” both of a military-technical and other nature, in order to stop threats to its national security rising.
Mr Zhuravlyov claimed Finland is being provoked into joining Nato by the US and the UK. “The Finns have nothing to share with us. They receive more than 90pc gas, timber and much more from us.
“Who needs fighting first of all? The Finns? They are not afraid that Russia is attacking them. Of course, sooner or later the Americans will force them to do so.
“Just as they forced Ukraine to do it, they are trying to force Poland and Romania. And, as practice shows, they succeed.”
Deputy foreign minister Alexander Grushko said Moscow will take adequate precautionary measures if Nato deploys nuclear forces and infrastructure closer to Russia’s border, according to the RIA news agency.
He added that Moscow has no hostile intentions towards Finland and Sweden and does not see “real” reasons for those two countries to be joining Nato alliance.
In an interview with many colourful remarks such as labelling Baltic nations Lithuania and Estonia, stink bugs, Mr Zhuravlyov also claimed that St Petersburg - Russian President Vladimir Putin’s birthplace - could be Nato’s first target in a war with Russia, adding that the US “will do everything possible to make World War III happen”.
“They [US] will be able to attribute all their problems to the war, as they already did in the First World War and the Second World War.
“They got out of their crisis only thanks to the war in Europe. But there is a big danger: who guarantees that nuclear missiles will not fly? I do not guarantee this.”
Meanwhile Finnish President Sauli Niinisto told Russian President Vladimir Putin by phone about Helsinki's plans to join Nato, Interfax news agency cited Bloomberg as saying on Saturday.
Russia has said Finnish entry to Nato poses a threat to which it will respond, but has not specified how.
Putin said a change in Finland’s foreign policy could be negative for bilateral relations.
Russian energy supplier RAO Nordic says it will suspend deliveries of electricity to Finland from Saturday, citing problems with payments as tensions between the two nations rise.
The Finnish grid operator said Russia provided only a small percentage of the country's electricity and that it could be replaced from alternative sources.
Fingrid said it did not expect electricity shortages as a result of the shut off, as only around 10pc of Finland's electricity is supplied from Russia.