Donald Trump made the comments during the MSNBC talk show Morning Joe.
The Republican leader sparked fears about a new global nuclear arms race on Thursday when he sent a tweet calling on the US to expand its nuclear arsenal.
He said the US must “greatly strengthen and expand” its stock of atomic weapons until “the world comes to its senses regarding nukes”.
Trump has issued no further details about his plans.
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.”
Trump’s comment immediately triggered fears that the next US president will reverse decades of policy in which the US has sought to reduce its nuclear arsenal.
Earlier Trump’s newly named press secretary, Sean Spicer, attempted to allay fears, saying in an interview on the “Today” show that “there is not going to be” an arms race.
“There’s not going to be [an arms race] because he is going to ensure other countries get the message, he is not going to sit back and allow that,” Spicer said. “What’s going to happen is they will all come to their senses and we will all be just fine.”
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.