"Many people have asked how we are doing in our negotiations with North Korea -- I always reply by saying we are in no hurry," he tweeted.

But Trump also expressed optimism, saying North Korea's economy has "wonderful potential" and that its leader Kim Jong Un "sees it better than anyone and will fully take advantage of it for his people."

A historic summit between Trump and Kim in June opened up dialogue on denuclearization of the Korean peninsula between the two countries after months of military threats.

A second summit is expected to be held next year, but Trump faces criticism given that North Korea has taken few concrete steps to abandon its nuclear and ballistic missile programs.

The Security Council has slapped a series of tough economic sanctions on Pyongyang over its nuclear tests and ballistic missile firings.

The United States maintains that UN sanctions will remain in place until North Korea has fully scrapped its weapons programs.