The chief of US naval operations said on Saturday fresh UN sanctions were preventing North Korea from transporting suspected weapons overseas, according to local media.
Admiral Gary Roughead, visiting Japan, noted that a North Korean ship tracked by the US Navy and suspected of transporting weapons has turned around because countries in the region were refusing its port call.
"What we are seeing is the effect of the UN Security Council Resolution that was put into effect," Roughead told local media, according to Japanese public broadcaster NHK.
Earlier this week, a Pentagon official said the Kang Nam 1, which had been reportedly bound for Myanmar with weapons or military technology, had turned back after the US Navy began tracking it.
Tougher sanctions, imposed in response to the North's May nuclear test, call on UN member states to inspect cargoes if they suspect they are banned weapons shipments to or from the North.
Pyongyang responded defiantly, vowing to build more nuclear bombs.
Japan, along with the United States, pushed hard for tough sanctions after the North's long-range rocket launch on April 5 and its second underground atomic test on May 25.