The White House on Thursday acknowledged that North Korea's nuclear accounting did not meet past US demands for a full detailing of alleged uranium enrichment or shared atomic know-how overseas.

"The accounting they have given is: 'We are not now engaged in any enrichment program or any proliferation activities and we will not in the future,'" said US national security adviser Stephen Hadley.

Repeatedly pressed on whether the secretive communist regime in Pyongyang had spelled out its past activities on both fronts, Hadley gave reporters variations on the same answer and said Washington still had concerns.

"The declaration they've made, with the disclosure they've made, is 'we're not engaged in this activity now. We'll not engage it in the future,'" and pledged to work on a structure for verifying their past activities, he said.

"And they have, as you've noticed, have not been out publicly denying that or discounting these concerns.

"So we're in the situation of not quite admitting, not denying, but opening the door for us to be able to try and get greater clarity," Hadley said.

The outstanding issues include Washington's charges that North Korea helped Syria start construction on a suspect nuclear site, which Israel destroyed in an air strike in September, he said. Syria denies the allegation.

"We want to get to the bottom of that so we understand what that activity was to make sure there is not continuing activity going on between North Korea and Syria or activity with respect to other locations, as well," said Hadley.

The State Department said however in a statement that North Korea had handed China "a package" of nuclear declarations which "addresses North Korea's uranium enrichment and proliferation activities" without giving any details.

North Korea will not be removed from the US terrorism list until a verification system is put in place and verification itself begins, the statement said.

"After a period of 45 calendar days and absent the enactment of a joint resolution blocking the proposed rescission, the secretary of state may rescind North Korea's designation as a state sponsor of terrorism on August 11," it said.