U.S. President Donald Trump has turned talk of a quick resolution to the denuclearization of North Korea on its head, saying Tuesday that there is "no time limit" for Pyongyang to relinquish its nuclear arsenal.

"Discussions are ongoing and they're going very, very well," Trump said in Washington.

"We have no time limit. We have no speed limit. ... We're just going through the process. But the relationships are very good," Trump said in Washington after his meeting with Russian President Vladimir Putin in Helsinki.