 -- Russian President Vladimir Putin responded today to comments by President-elect Donald Trump that America needs to greatly strengthen its nuclear capabilities.

“There’s nothing new about it,” Putin said, answering a question at his lengthy press conference that he gives at the end of every year in Moscow. “He declared the need for strengthening the nuclear element of the United States, the strengthening of the armed forces during his election campaign. There is nothing unusual about it."

On Thursday, Trump caused some alarm and surprise when he wrote on his Twitter account that the U.S. “must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes.”

That sentence was immediately criticized by some as potentially starting a new nuclear arms race in the world by upending decades of U.S. policy that seeks to reduce the number of nuclear weapons globally.

Trump's tweet appeared to be a response to Putin, who a few hours before had told a group of military officials that Russia must develop a new generation of nuclear weapons that can “reliably penetrate any existing and prospective missile defense systems,” a possible reference to efforts by the U.S. to develop a missile-defense shield in eastern Europe.

A spokesman for Trump's transition team said the tweet was meant to express the threat posed by nuclear proliferation.

In his press conference today, Putin said that modernization was intended to give Russia a superiority only against “an aggressor.”

“It’s very important. I didn’t say that accidentally, Putin said. "What is an aggressor — it’s someone who can potentially attack Russia. We are stronger than any potential aggressor."

"If someone wants to launch an arms [race], it's not us," Putin continued.

Both Russia and the U.S. are already engaged in large-scale programs to modernize their nuclear arsenals, which still often rely on Cold War-era systems. It was unclear if Trump's tweet simply indicated support for the American side of these efforts or if he was calling for more.

President Obama has been a vocal advocate of nuclear arms control, hosting four international summits on nuclear proliferation in his tenure, but he has had little success in deepening cooperation with Russia on the issue. Moscow boycotted the last summit amid a climate of exceptional hostility with the U.S.

Putin made it clear to reporters that he looked forward to an improvement of relations with the incoming Trump administration.

"Mr. Trump said during the election campaign there would be no further exacerbation because it was already worse than ever, and I agree with him,” Putin said. “Together we will think on ways to achieve an improvement."

He also laughed off accusations from U.S. intelligence agencies that Russia had interfered in the U.S. election.

“The losing side always looks for those to blame on the outside,” Putin said. “They’re losing on all fronts. All fronts," he said referring to the Democratic Party and the Obama administration.