Trump's comments echoed statements he offered in December when he tweeted about "expand[ing]" the nation's "nuclear capability" and told MSNBC that he was willing to engage in an "arms race."
"The U.S. will not yield its supremacy in this area to anybody," said Spicer. "That’s what he made very clear [during the interview], and that if other countries have nuclear capabilities, it’ll always be the United States that [has] the supremacy and commitment to this."
On Dec. 22, Trump -- who indicated during the campaign that some nuclear proliferation might be good -- advocated in a tweet for bolstering American capabilities.
The next day, speaking by phone to Mika Brzezinski, the co-host of MSNBC's "Morning Joe," Trump said he'd be open to competing with other countries to accumulate weapons.
“Let it be an arms race,” said Trump. “We will outmatch them at every pass and outlast them all.”
In Thursday's Reuters interview, Trump brought up both Russian cruise missile usage and North Korean missile tests and told the news outlet that the U.S. "has fallen behind in its atomic weapons capacity."