U.S. Secretary of State Confoleezza Rice (file photo)

U.S. Secretary of State Condoleezza Rice says substantive differences remain between Washington and Pyongyang over North Korea's overdue nuclear declaration.

Secretary Rice spoke Friday, one day after the top U.S. envoy for the North Korean nuclear talks met with his counterpart from Pyongyang in Geneva.

Rice said the envoys have reported the discussions to their respective capitals, but she does not expect any immediate breakthrough.

The secretary of state said the United States is prepared to meet its obligations to North Korea under a deal reached last year. She said North Korea must fulfills its obligations, which include declaring all of its nuclear activities and stockpiles.

The United States is demanding that North Korea account for uranium enrichment that it has never publicly acknowledged.

U.S. Assistant Secretary of State Christopher Hill said his talks with North Korean envoy Kim Kye Kwan brought progress. But he did not report any breakthrough on Pyongyang's delayed nuclear declaration. The envoys held two closed-door meetings Thursday in Geneva.

Under a six-nation deal, Pyongyang was supposed to provide a list of all of its nuclear programs by the end of last year, but Washington says the list was not complete.

The six-party talks, which include the U.S., China, Japan, Russia and North and South Korea, began five years ago in an effort to get Pyongyang to end its nuclear weapons program in exchange for diplomatic benefits and energy aid.