North Korea has at least one more secret uranium enrichment facility, South Korean and U.S. believe. They believe that this is the reason Pyongyang has agreed in recent talks with Washington to allow the International Atomic Energy Agency to inspect its first uranium enrichment plant in Yongbyon in return for the resumption of aid.

"It's clear that the North has other uranium enrichment facilities in several places besides Yongbyon," a South Korean government official said on Thursday. "The regime is probably going to use the Yongbyon plant as a showcase."

The North used plutonium extracted from a now defunct 5-megawatt reactor at Yongbyon as a bargaining chip in negotiations with the U.S. in the late 1990s and is now probably trying to use the same trick with its uranium enrichment program.

The regime denied the existence of the uranium plant until it suddenly showed the facility to a visiting U.S. nuclear scientist in 2010. In a statement on Wednesday released simultaneously with the U.S., the North said it will allow IAEA inspectors access to the facility at Yongbyon.

A senior Cheong Wa Dae official said, "The issue of the other uranium enrichment facilities the North hasn't disclosed also needs to be resolved." He added Seoul still supports the "grand bargain" proposed by President Lee Myung-bak whereby the North can expect massive economic aid if it completely abandons its nuclear program.

Seoul and Washington reportedly know where some of the other uranium enrichment plants are and will bring this issue once six-party nuclear disarmament talks resume.

The IAEA said it is ready to inspect the North's nuclear facilities in accordance with the Washington-Pyongyang agreement. Pyongyang threw IAEA inspectors out in April 2009. They will return late this month or early next month.