The authorities in China had earlier said the magnitude 3.4 quake was a "suspected explosion", while South Korea's weather agency took the view it was triggered naturally. "The depth is poorly constrained and has been held to 5 km by the seismologist", USGS said in a statement.
U.S. President Donald Trump called the North Korean leader a "madman" on Friday, a day after Kim dubbed him a "mentally deranged U.S. dotard" who would face the "highest level of hard-line countermeasure in history".
Regional experts differed on their analysis of the tremor, with China's China Earthquake Network Centre (CENC) service calling it a "suspected explosion", while Seoul's Korea Meteorological Agency (KMA) judged it a "natural quake".
All of North Korea's previous six nuclear tests registered as earthquakes of magnitude 4.3 or above.
The official reportedly said that the measures will now be prepared in detail to be formally approved at a meeting of European foreign ministers next month.
Seismic activity was detected Saturday near the site of North Korea's Punggye-ri nuclear site, but it is not known whether a nuclear test caused the development.
A secondary tremor detected after that test could have been caused by the collapse of a tunnel at the mountainous site, experts said at the time. North Korea has one nuclear test site - Punggye-ri.
Another official at the the Korea Meteorological Administration's command center said it is believed to have been a natural quake.
China also will ban textile imports from the North, the ministry said.
China has announced it will limit oil exports to North Korea under United Nations sanctions over its nuclear and missile development, further reducing support from Pyongyang's last major trading partner, energy supplier and diplomatic ally.
Quoting an EU official on Thursday, AFP reported that ambassadors from the 28 member states on Thursday "agreed on a package of new autonomous measures", including a ban on investments in North Korea and a symbolic ban of European Union exports of oil, as the EU doesn't actually export any oil to the North.
The Sept. 3 detonation followed two intercontinental ballistic missile launches in July that brought Kim Jong Un's isolated regime a step closer to achieving its aim of being able to deploy a nuclear warhead over the continental U.S.
Earlier on Saturday, China said it will limit exports of refined petroleum products from October 1 and ban exports of condensates and liquefied natural gas immediately to comply with the latest United Nations sanctions.