Pyongyang would be watching Washington's moves closely, Japanese media quoted Kim as saying.
He refused to discuss the country's weapons until Washington made the first move.
Kim was in New York this week for the first meeting of the US-North Korea Working Group, one of five that were established under the February six-party accord.
North Korea agreed on February 13 to meet a 60-day deadline for disarming its nuclear weapons programme and allow inspectors back in.
In exchange, it was promised aid equal to 50,000 tonnes of heavy fuel oil from the other signatories – the US, South Korea, Russia, China and Japan.