Trump calls for expanding US nuclear weapons

US President-elect Donald Trump called on Thursday for the country to expand its nuclear weapons capabilities until the world "comes to its senses" - a signal he may support costly efforts to modernize the aging US nuclear arsenal.

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".

In a post on Twitter, Trump said, "The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes."

Trump, who is in Florida for the Christmas holiday, gave no further details. Asked about the tweet, a spokesman said later 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 also has "emphasized the need to improve and modernize our deterrent capability as a vital way to pursue peace through strength," spokesman Jason Miller said.

During the next decade, US ballistic missile submarines, bombers, and land-based missiles - the three legs of the nuclear triad - are expected to reach the end of their useful lives. Maintaining and modernizing the arsenal is expected to cost at about $1 trillion dollars over 30 years, according to independent estimates.

Putin, who has said that Trump has confirmed to him he is willing to mend ties between the two countries, spoke on Thursday of the need to enhance the country's nuclear arsenal.

"We need to strengthen the military potential of strategic nuclear forces, especially with missile complexes that can reliably penetrate any existing and prospective missile defense systems," he said in a speech in Moscow.

Trump, who takes office on Jan 20, campaigned on a platform of building up the military, but also pledged to cut taxes and control spending. He has also said he wants to improve relations with Russia.

Trump met on Wednesday with a dozen Pentagon officials involved with defense acquisition programs, as well as the chief executives of Lockheed Martin Corp and Boeing Co, the country's two largest defense contractors.

Trump said he talked with the CEOs about lowering costs for two high-profile programs: Lockheed Martin's F-35 fighter jets and Boeing's replacement 747-8s for the presidential Air Force One plane.

The United States is one of five nuclear weapons states allowed to keep a nuclear arsenal under the Nuclear Non-Proliferation Treaty. The others are Russia, Britain, France and China.

Most of the US arsenal was built between 25 and 62 years ago during the arms race with the former Soviet Union, and has been patched and otherwise refashioned many times to extend its lifespan.