"We're certainly aware of those reports that have come out. That's an issue that we would take very seriously if that were to be the case," Nauert told reporters. "As a general matter we don't comment on intelligence reports. Ukraine, though, we have to say has a very strong non-proliferation record, and that includes specifically with respect to the DPRK."
The State Department spokesperson was referring to a report in the New York Times on Monday that said Pyongyang may be using engines from Ukraine for its missiles.
Nauert noted that United Nations Security Council resolutions obligate all nations, including Ukraine, to prevent transfers of sensitive technology to Ukraine.
She added that in the past, Kiev has prevented shipments of sensitive materials to nations where such transfers would raise concerns.
The article, which cited a classified assessment by US intelligence agencies, as well as a recent study by Michael Elleman, senior fellow for missile defense with the International Institute for Strategic Studies, suggested that Pyongyang may be using a modified RD-250 high-performance liquid-propellant engine (LPE) for its latest missiles.
The same types of missiles were in the past developed at Ukraine's state-owned Yuzhmash and Russia’s Energomash company. The article quoted Elleman as saying that the engines for the North Korean missiles probably came from Ukraine illicitly.