Florida: President-elect Donald Trump welcomed on Friday a new nuclear weapons arms race with Russia, vowing in an off-camera interview with a television host that America would "outmatch" any adversary.

The comment came one day after he said in a post on Twitter that the United States should "strengthen and expand" its own nuclear capabilities.

The president-elect escalated his comments about nuclear weapons with the show of bravado during a brief, off-air telephone conversation from his estate in Florida, according to Mika Brzezinski, the co-host of MSNBC's "Morning Joe" program.

"Let it be an arms race," Trump said, according to Brzezinski, who described her conversation with the president-elect on the morning news program moments later. Trump added: "We will outmatch them at every pass and outlast them all."

Taken at face value, the comment appears to reflect a willingness on Trump's part to restart the costly and dangerous Cold War-era nuclear weapons competition between the United States and the old Soviet Union. Both nations have sought for decades to reverse that buildup of huge nuclear arsenals.

Friday's comments and Thursday's Twitter post appeared to be meant specifically for Russian President Vladimir Putin, who had said in an end-of-the-year speech to his military this week that Russia must bolster its nuclear capabilities to "reliably penetrate" missile defense systems of any other nation.

Putin said during a lengthy news conference in Moscow on Friday that Russia would continue to modernise its armed forces, including nuclear weapons. Russia is not seeking a new arms race or to develop new nuclear warheads, he said, but is instead seeking ways to improve its armaments so that they could pierce US missile defenses.

Trump has not provided any details about his plans regarding an expansion of nuclear capabilities, but Sean Spicer, the incoming press secretary in Trump's administration, said earlier on the "Morning Joe" program that the president-elect's Twitter post about nuclear weapons on Thursday was intended to send a message to America's adversaries around the world.

Asked if Trump's post on Twitter was a response to Putin's speech to the military, Spicer said, "I think it's putting every nation on notice that the United States is going to reassert its position in the globe."

Spicer added: "Other countries need to understand that if they expand their nuclear capabilities, this president is not going to sit back; he's going to act."

Friday morning's comments by Trump and Spicer about the president-elect's intentions regarding the nuclear arsenal stood in contrast to what other aides said late Thursday. Jason Miller, the incoming communications director, said in a statement that Trump's post on Twitter was about the spread of nuclear capabilities around the globe.

"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," Miller wrote.

Kellyanne Conway, who will become counselor to the president in the White House, appeared on "The Rachel Maddow Show" on MSNBC on Thursday evening and downplayed the significance of Trump's post.

"I don't think the tweet was groundbreaking in this regard. It seems that President Obama himself has invested, has called for an upgrade in our capabilities," Conway said.

Referring to Trump, she said, "I think in his quest to keep us safe and secure, he's putting the world on notice that he will do what he thinks he needs to do to keep us safe and secure."

The New York Times