Yu Myung-hwan's statement came after an announcement by Chinese Deputy Foreign Minister Wu Dawei that Pyongyang would hand over the long-delayed nuclear declaration to China later on Thursday.
"North Korea handed its nuclear declaration over to Beijing in the second part of the day," Yu said.
A White House statement said the North was set to demolish the cooling tower at its Yongbyon nuclear complex on Friday.
"The weapons and all the programs are going to have to be dealt with and dismantled if we are to have denuclearization and it's going to have to be done so verifiably," U.S. Secretary of State Condoleezza Rice said in Kyoto, Japan, where she was attending a meeting of G8 foreign ministers.
Pyongyang missed a deadline for submitting the data late last year, causing six-nation talks involving China, Japan, Russia, the U.S. and the two Koreas to stall. Pyongyang also agreed in February 2007 to halt its nuclear programs in return for economic aid and diplomatic incentives.
The Chinese deputy minister also said the United States had agreed to remove North Korea from the blacklist of countries supporting terrorism in exchange for Pyongyang handing over details of its nuclear program.
"The U.S. administration has made a decision to launch procedures to strike North Korea off the list of countries sponsoring terrorism," Dawei said.
U.S. President George Bush said on Thursday that the handing over of the declaration and the removal of North Korea from the blacklist marked the start of a process of "action for action."
Inclusion on the blacklist prevents North Korea from receiving low-interest World Bank loans. It also prevents the country from receiving loans from other international lending agencies.
Beijing has hosted the six-party talks since August 2003.
