"We have had no missile launches or provocative acts on the part of North Korea since the unanimous adoption of the UN Security Council resolution," he said.
This, he said, could pave the way for talks between the two sides "sometime in the near future".
The US Office of Foreign Assets Control designated 10 companies and six individuals in its sanctions.
"[The] Treasury will continue to increase pressure on North Korea by targeting those who support the advancement of nuclear and ballistic missile programmes, and isolating them from the American financial system," said Treasury Secretary Steven Mnuchin.
The action means American individuals and companies are no longer permitted to do business with these firms.
China responded swiftly, calling on the US to "immediately correct its mistake" of punishing its firms.
A series of missile tests by North Korea in recent months - along with its repeated threats to carry out a sixth test of a nuclear device - have increased tensions between Pyongyang and the US.
North Korea has been angered, as it is every year, by scheduled US-South Korea military drills, and threatened to launch missiles near the US island of Guam in the South Pacific.
US President Donald Trump, meanwhile, threatened the isolated regime with "fire and fury like the world has never seen".
In North Korea’s latest propaganda video, released on Tuesday, an image of Mr Trump is shown at a cemetery which is apparently meant to be in Guam.