U.S. President Donald Trump on Thursday escalated his threat to the Democratic People' s Republic of Korea (DPRK), saying maybe his previous warning "wasn't tough enough."

"Frankly, the people who were questioning that statement, was it too tough? Maybe it wasn't tough enough," he told reporters in his golf resort in New Jersey.

"They've been doing this to our country for a long time, for many years, and it's about time that somebody stuck up for the people of this country and for the people of other countries. So if anything, maybe that statement wasn't tough enough," Trump added.

The U.S. President, despite the harsh rhetoric, offered assurance to the public, saying that the American people "should be very comfortable."

"If North Korea (DPRK) does anything in terms of even thinking about attack of anybody that we love or we represent or our allies or us... they should be very nervous," Trump said. "Because things will happen to them like they never thought possible."

On Tuesday, Trump issued a controversial warning to the DPRK that appeared to threaten a nuclear war with the Asian country.

"North Korea (DPRK) best not make any more threats to the United States. They will be met with fire and fury like the world has never seen," Trump said.

In response, the DPRK warned of preemptive strikes against the U.S. military base of Guam in the Pacific.

Following the exchange of fierce rhetoric between Washington and Pyongyang, U.S. Secretary of State Rex Tillerson on Wednesday played down the threat from the DPRK, telling Americans to "sleep well at night."