Trump calls for increased US nuclear capabilities

America must massively boost its nuclear capability until the "world comes to its senses," President-elect Donald Trump said Thursday, hours after a similar vow by Russia's Vladimir Putin.

Trump made the statement on Twitter, saying that "the United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes," without providing details or context. The tweet came a day after meeting a group of Pentagon top brass, and shortly after Putin called for Russia to reinforce its own nuclear capabilities.

The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes

— Donald J. Trump (@realDonaldTrump) December 22, 2016

It was not clear what prompted his comment. However, earlier on Thursday, Russian President Vladimir Putin said that Russia needed to "strengthen the military potential of strategic nuclear forces."

Asked about the tweet, Trump spokesman Jason Miller later said Trump was "referring to the threat of nuclear proliferation and the critical need to prevent it - particularly to and among terrorist organizations and unstable and rogue regimes."

Trump, who takes office on 20 January, also has "emphasised the need to improve and modernise our deterrent capability as a vital way to pursue peace through strength," Miller said.

Miller told Reuters that Trump was not advocating the use of nuclear weapons, and said Trump's comments were not meant to be read as a new policy proposal.

On Wednesday Trump met with a group of Pentagon brass including Vice Admiral James Syring, who heads the Missile Defence Agency.

Their conversations centred on cutting costs to various military programmes, and it was not known if Trump's tweet was triggered by information the incoming President gleaned from the US officials, or by Putin's comments.

America currently has an estimated arsenal of about 7,000 nuclear warheads, second only to Russia, which has a few hundred more.