Trump made the comments to reporters while departing leaving his Mar-a-Lago resort in Florida, where he spends nearly every weekend.
Last week, Tillerson issued the Trump administration's starkest warning yet to North Korea, saying a military response would be "on the table" if it took action to threaten South Korean and United States forces. "I will tell you, he's acting very badly", Trump said.
Separately, the United States is not sure whether North Korea's military is capable of miniaturizing a nuclear warhead so that it could be mounted on a rocket, such as an ICBM, though Pyongyang has claimed this capability and USA officials have said that they incorporate that ability in their planning assumptions. A successful test would indicate that North Korea is increasingly capable of firing a long-range missile.
The country tested at least five missile launches since President Donald Trump was elected in 2016. Of the North Korean rocket and missile projects that we are now aware of, the best fit for this engine would be as the second stage of the new satellite launch vehicle provisionally known as the "Unha-9".
Last month, Reuters reported that North Korean intelligence ran an arms operation out of Malaysia called Glocom, using two front companies identified as International Global System and International Golden Services.
North Korea continues its new practice of releasing colorful audiovisual presentations of Kim Jong Un watching ground tests of rocket hardware, presumably as a way of signaling constant progress in the development of North Korean space and missile systems.
Theresa May says she will trigger Brexit next Wednesday
A spokesperson for the European Commission said it was "ready to begin negotiations" and it had "everything ready and decided". Tim Farron, leader of the Liberal Democratic Party, said, "Theresa May is embarking on an extreme and divisive Brexit".
"If they elevate the threat of their weapons program to a level that we believe requires action, that option is on the table", the top USA diplomat said in a comment widely interpreted to refer to the possibility of pre-emptive military force.
North Korea media slammed the United States for allegations Pyongyang may be behind a wave of cyberattacks against worldwide banks and other institutions.
Past US administrations have considered military force against North Korea over its development of nuclear weapons and ballistic missiles, but rarely has that option been expressed so explicitly.
Sunday's test was a "precisely-timed spectacular", said Peter Hayes, director of the US-based Nautilus Institute, "the kind we've come to expect from Kim Jong Un".
In a UNSC report, Malaysia Korea Partners Holdings (MKP) was being probed for establishing the International Consortium Bank (ICB) in Pyongyang, via a joint venture.
The test coincided with Mr Tillerson's visit to Asia. However, analysts have long accused Pyongyang of using the program as a covert weapons testing scheme.