Exclusive - Trump wants to expand U.S. nuclear arsenal, make it 'top of the pack'

U.S. President Donald Trump is interviewed by Reuters in the Oval Office at the White House in Washington, U.S., February 23, 2017. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - President Donald Trump said on Thursday he wants to ensure the U.S. nuclear arsenal is at the "top of the pack," saying the United States has fallen behind in its weapons capacity.

In a Reuters interview, Trump also said China could solve the national security challenge posed by North Korea "very easily if they want to," ratcheting up pressure on Beijing to exert more influence to rein in Pyongyang's increasingly bellicose actions.