Washington: Donald Trump and Vladimir Putin have fired the starting gun on a new nuclear arms race as they both vowed to launch a major strengthening of their countries' arsenals.
Mr Trump, the US President-elect, said on Twitter: "The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes."
More World News Videos
Putin suspends nuclear pact
Russian President Vladimir Putin calls off a 2010 treaty with the US to dispose of weapons-grade plutonium.
That appeared to be a response to sabre-rattling remarks hours earlier by Mr Putin.
Speaking at an end-of-year meeting with his defence chiefs, the Russian President said bolstering nuclear capability should be a chief objective for 2017.
"We need to strengthen the military potential of strategic nuclear forces, especially with missile complexes that can reliably penetrate any existing and prospective missile defence systems," Mr Putin said on Thursday.
He added: "We must carefully monitor any changes in the balance of power and in the political-military situation in the world, especially along Russian borders, and quickly adapt plans for neutralising threats to our country.
"We can say with certainty we are stronger now than any potential aggressor. Anyone."
Russia and the US jointly account for more than 90 per cent of the world's nuclear weapons, fielding an estimated 7300 and 7100 respectively.
![President-elect Donald Trump has signalled an apparent reversal of a decades-long reduction of the nation's atomic weapons.](/web/20161223084635im_/http://www.smh.com.au/content/dam/images/g/t/g/x/g/r/image.related.articleLeadwide.620x349.gtgxl8.png/1482452585073.jpg)
Both countries' arsenals are regulated by a series of bilateral arms limitation treaties that place strict limits on the numbers and kinds of warheads and delivery systems they can field.
A rapid expansion of either nation's forces could shatter that arms control regime and plunge the world back into an era of Cold-War style nuclear arms race.
![President Barack Obama has reduced the US nuclear arsenal.](/web/20161223084635im_/http://www.smh.com.au/content/dam/images/g/t/f/8/p/p/image.related.articleLeadwide.620x349.gtgxl8.png/1482452585150.jpg)
Mr Trump's statement marked a jarring departure from President Barack Obama's position on the nuclear issue. In a speech in Prague in 2009, Mr Obama called for the elimination of nuclear weapons.
Mr Trump's announcement came the day after he met eight generals and admirals in a military summit at his Mar-a-Lago estate in Florida.
He made a series of aggressive statements about nuclear weapons during the election campaign, saying: "I'm not going to take cards off the table. We have nuclear capability."
At one point, he also said America would be "better off" if such countries as Japan, South Korea and Saudi Arabia developed their own nuclear weapons.
Hillary Clinton repeatedly questioned Mr Trump's temperament and his fitness to be in possession of the detonation codes.
Ten former launch operators wrote a protest letter asserting he did not have the diplomatic skills to avoid a nuclear war.
According to his website, Mr Trump "recognises the uniquely catastrophic threats posed by nuclear weapons" and his stated policy is to modernise the nuclear arsenal "to ensure it continues to be an effective deterrent".
Following his latest statement, there was an immediate surge in shares of companies producing uranium amid anticipation of more demand for it in the nuclear program.
Over the next three decades, the Pentagon is expected spend $1 trillion upgrading its nuclear weapons systems.
Russia is in the midst of a multi-year nuclear upgrade program, with new strategic missile submarines, upgraded strategic bombers, and new intercontinental ballistic missiles all under production.
"In this sense, Russia is one step ahead of the United States," said Igor Sutyagin, an expert on the Russian military at the Royal United Services Institute.
However, Mr Sutyagin cautioned that Russia would be alarmed at the prospect of entering a Cold War-style bomb-building race, because the cost would be prohibitive and the US would probably quickly outstrip Russian production.
"That's why these arms control treaties have lasted as long as they have - Russia is more interested in maintaining them than the United States," he said.
"Mr Putin will be very, very worried about statements like this coming from Washington," he added.
There was also confusion over whether Mr Trump's statement was a call to increase the number of America's nuclear warheads, or referred to modernising existing systems. There was no immediate clarification from the Trump team.
Daryl Kimball, executive director of the Arms Control Association, said: "Trump and his people need to explain the basis of his cryptic tweet. What does he mean by expand, and at what cost? He will be shocked by the skyrocketing costs of the current plan to modernise the US nuclear arsenal."
Retired general James "Spider" Marks, a 30-year US army veteran, voiced disquiet over Mr Trump discussing nuclear issues on social media. He said: "That's very concerning to me. It concerns me that our President-elect would do that."
In a statement, Trump spokesman Jason Miller said: "President-elect Trump was referring to the threat of nuclear proliferation and the critical need to prevent it - particularly to and among terrorist organisations and unstable and rogue regimes. He has also emphasised the need to improve and modernise our deterrent capability as a vital way to pursue peace through strength."
Telegraph, London