(CNN) President-elect Donald Trump signaled Thursday that he will look to "strengthen and expand" the US's nuclear capability hours after Russian President Vladimir Putin pledged to enhance his country's nuclear forces.

The exchange appeared to raise the prospect of a new arms race between the two nuclear superpowers, which between them boast more than 14,000 nuclear warheads, the still deadly legacy of their four-decades long Cold War standoff.

But the comments by Putin, who is presiding over a project to restore Russia's lost global power and influence, and Trump, who will shortly become the US commander-in-chief, did not spell out exactly what each side is proposing or whether a major change of nuclear doctrine is in the offing.

Trump weighed in with a tweet just hours after Putin spoke following a meeting with his military advisers to review the activity of the past year.

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

On Friday, Putin downplayed the risk of a new nuclear arms race between Russia and the US and said there was "nothing new" in Trump's tweet.

"During his election campaign, (Trump) said US needs to bolster nuclear capabilities and armed forces in general and there is nothing new," Putin said at this annual news conference.

It was not immediately clear if the President-elect is proposing an entire new nuclear policy that he would begin to flesh out once he takes office next year.

Trump could also be referring to plans to modernize the current US nuclear arsenal that are currently underway and will cost hundreds of billions of dollars. The Obama administration has outlined a plan to modernize delivery systems, command and control systems and to refurbish warheads in the US nuclear triad -- the US force of sea, airborne and missile delivered nuclear weapons.

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But the plan keeps the size of the nuclear force at existing levels.

Trump's tweet appeared to envisage an expansion of the size of the US nuclear force, but it was not immediately clear if that is the case.

Trump communications director Jason Miller sent a statement to try to explain the President-elect's tweet on nuclear capability.

He suggested Trump was "referring to the threat of nuclear proliferation and the critical need to prevent it," although that was not referenced in the tweet. He also said Trump was emphasizing the need to "modernize our deterrent capability."

In Moscow earlier Tuesday, Putin said in a defense speech that Russia needs to "enhance the combat capability of strategic nuclear forces, primarily by strengthening missile complexes that will be guaranteed to penetrate existing and future missile defense systems."

Putin's remarks appeared to suggest that he was talking about new weapons systems that could overcome US missile defenses, a development that could force the US to respond. It was not clear, however, if he was contemplating an expansion in the total numbers of Russian weapons or of the stocks of those arms that are deployed.

Trump and Putin have suggested Trump's inauguration next month will ring in closer relations after the two sides retreated to their most entrenched positions since the end of the Cold War.

The ambiguity and timing of Putin's remarks also suggested that he may be laying an opening gambit in his relationship with the new US President-elect.

The Russian President is seeking to return Russia to the front ranks of global influence, a project that is key to his domestic political survival and often involves actively seeking to undermine US power.

His power plays in Ukraine and in Syria and military maneuvers close to the borders of former Warsaw Pact states have alarmed Western leaders and stoked tensions in Europe.

Photos: Cult of Putin Photos: Cult of Putin Putin plays with his Yume, an Akita dog, prior to an interview by Nippon Television Network Corporation on December 7, 2016. Hide Caption 1 of 24 Photos: Cult of Putin Putin visits Russia's Przewalski horse reintroduction center in the Orenburg Reserves, near the border with Kazakhstan, on October 3, 2016. Hide Caption 2 of 24 Photos: Cult of Putin While his nation waded deeper into the Syrian civil war, Russian President Vladimir Putin, right, spent his 63rd birthday on the ice Wednesday, October 7, playing hockey with NHL stars and various Russian officials and tycoons in Sochi. For years, Russia's leader has cultivated a populist image in the Russian media. Hide Caption 3 of 24 Photos: Cult of Putin Putin holds a cat as he inspects housing built for victims of wildfires in the village of Krasnopolye, in a region in southeastern Siberia, Russia, on Friday, September 4. Hide Caption 4 of 24 Photos: Cult of Putin Putin, left, and Prime Minister Dmitry Medvedev jokingly toast at a lunch during a meeting at the Black Sea resort in Sochi, Russia, on Sunday, August 30. Hide Caption 5 of 24 Photos: Cult of Putin Putin exercises during his meeting with Medvedev on August 30. Hide Caption 6 of 24 Photos: Cult of Putin Putin sits in a bathyscaphe as it plunges into the Black Sea along the coast of Sevastopol, Crimea, on Tuesday, August 18. Putin went underwater to see the wreckage of an ancient merchant ship that was found in the end of May. Hide Caption 7 of 24 Photos: Cult of Putin Putin holds a Persian leopard cub in February 2014 at a breeding and rehabilitation center in the Black Sea resort of Sochi. Perhaps the most important vote in Russia's public selection of a new Olympic mascot was cast when Putin said he wanted a funky leopard to represent the 2014 Sochi Winter Games. Hide Caption 8 of 24 Photos: Cult of Putin Putin holds a pike he caught in the Siberian Tuva region of Russia on July 20, 2013. Hide Caption 9 of 24 Photos: Cult of Putin Putin enjoys some fishing during his vacation to the Tuva region on July 20, 2013. Hide Caption 10 of 24 Photos: Cult of Putin Putin submerges on board Sea Explorer 5 bathyscaphe near the isle of Gogland in the Gulf of Finland on July 15, 2013. Hide Caption 11 of 24 Photos: Cult of Putin Putin plays with his dogs 'Buffy', right, and 'Yume' at his residence Novo-Ogariovo, outside Moscow, on March 24, 2013. Hide Caption 12 of 24 Photos: Cult of Putin Putin studies a crane during an experiment called Flight of Hope on September 5, 2012, in which he piloted a hang glider, aiming to lead the birds into flight. It's part of a project to save the rare species of crane. Hide Caption 13 of 24 Photos: Cult of Putin Putin takes part in a training session for young ice hockey players before the "Golden Puck" youth tournament final in Moscow on April 15, 2011. Hide Caption 14 of 24 Photos: Cult of Putin Putin rides a Harley-Davidson to an international biker convention in southern Ukraine on July 14, 2010. Hide Caption 15 of 24 Photos: Cult of Putin The Russian president aims at a whale with an arbalest (crossbow) to take a piece of its skin for analysis at Olga Bay on August 25, 2010. Hide Caption 16 of 24 Photos: Cult of Putin A wetsuit-clad Putin embarks on a dive to an underwater archaeological site at Phanagoria on the Taman Peninsula on August 10, 2011. Hide Caption 17 of 24 Photos: Cult of Putin Famed for his love of martial arts, Putin throws a competitor in a judo session at an athletics school in St. Petersburg on December 18, 2009. Hide Caption 18 of 24 Photos: Cult of Putin Putin during his vacation in southern Siberia on August 3, 2009. Hide Caption 19 of 24 Photos: Cult of Putin Putin swims the butterfly during his vacation outside the town of Kyzyl in southern Siberia on August 3, 2009. Hide Caption 20 of 24 Photos: Cult of Putin Assisted by a Russian scientist, Putin fixes a satellite transmitter to a tiger during his visit to the Ussuriysky forest reserve of the Russian Academy of Sciences in the Far East on August 31, 2008. Hide Caption 21 of 24 Photos: Cult of Putin Putin carries a hunting rifle in the Republic of Tuva on September 3, 2007. Hide Caption 22 of 24 Photos: Cult of Putin A shirtless Putin fishing in the headwaters of the Yenisei River in the Republic of Tuva on August 13, 2007. Hide Caption 23 of 24 Photos: Cult of Putin Putin in the cockpit of a Tupolev Tu-160 strategic bomber jet at a military airport on August 16, 2005, before his supersonic flight. Hide Caption 24 of 24

And while Russia's economic and conventional military strength pales beside that of the US, its nuclear arsenal remains the root of its power and prestige.

It is also unlikely to be a coincidence that Putin's remarks came three days before the 25th anniversary of the fall of the Soviet Union, a collapse he views as a disaster of history.

Trump, who sees foreign policy through the eyes of an ultimate deal maker, may have felt the need to respond to Putin's remarks. He did so a day after meeting with his incoming military officials at his Mar-a-Lago resort in Florida. CNN's Barbara Starr reported that the talks included discussion of plans to modernize the US nuclear arsenal.

The President-elect's choice of Twitter to make such an important and sensitive statement was characteristic of his operating style.

But it underlined how the shorthanded communication of policy by social media is imprecise and open to multiple interpretations that are already posing problems for foreign governments as they seek to divine Trump's true intentions.

Still, the suggestion that he could preside over a new nuclear arms race will spook critics who argued he showed himself unfamiliar with basic nuclear doctrine during the campaign.

Democratic nominee Hillary Clinton had argued that it would be a mistake to hand the US nuclear codes over to a man who could be "baited with a tweet."

The President-elect also caused consternation in Asia by suggesting that Japan and South Korea who are protected under the US nuclear umbrella might think about developing their own weapons, a move that could unleash a new global nuclear arms race.

Trump's comment on Twitter also strikes a sharp contrast with the early months of the administration of President Barack Obama, who committed himself to the symbolic goal of a world without nuclear weapons -- an act that helped him win the Nobel Peace Prize.

Obama also concluded a new Strategic Arms Limitation Treaty (START) with Putin's predecessor as Russian President, Dmitry Medvedev. The treaty imposed new limits on the numbers of launchers and warheads each side have deployed.

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During the campaign, Trump argued that the US needs to modernize its aging nuclear infrastructure.

"Our nuclear program has fallen way behind, and they've gone wild with their nuclear program. Not good. Our government shouldn't have allowed that to happen," Trump said during his second debate in October against Clinton. "We are old. We're tired. We're exhausted in terms of nuclear. A very bad thing."

America's nuclear submarines are all more than 30 years old and its most dominant long-range bomber remains the 60-year-old B-52s. The Pentagon has also called for upgrading the US arsenal of ICBMs, or intercontinental ballistic missiles.

The Pentagon has estimated that it will need to spend as much as $18 billion per year over the next 15 years -- for a total of $270 billion -- to modernize the nuclear triad.

The United States has 7,100 nuclear warheads while Russia has 7,300, according to the non-partisan Arms Control Association.

The US has 1,367 warheads deployed on inter-continental ballistic missiles, heavy bombers and on submarines, the State Department said in September. Russia has 1,796 in the same category.

Russia's inventory of deployed warheads has risen in number owing to fluctuations in Moscow's modernization program and is not seen as a strategic worry by the US military. The United States currently has fewer total weapons, including those in reserve, than Russia because it has dismantled more obsolete devices.