Shortly after arriving in Seoul, U.S. Secretary of State Condoleezza Rice (search) got a chilling firsthand look at what a war on the Korean peninsula might look like as she prepared for Sunday talks with South Korean leaders to discuss the North's nuclear ambitions.

Rice became the most senior American (search) official to tour a command center for U.S. and South Korean troops that would be the battle headquarters in the event of fighting with the communist North.

"I know that you face a close-in threat every day," Rice told troops at Command Post Tango, or Theater Air Naval Ground Operations (search) late Saturday.

Rice's visit coincided with a twice-yearly war exercise involving thousands of American and South Korean soldiers. When Rice got a look at the command center, it also was the first time that reporters and cameras were allowed into the bunker south of Seoul.

North Korea denounced the exercises as a rehearsal for a U.S.-led pre-emptive attack.

"The Republic of Korea, a great democracy now, faces a threat across the divide of a state that is not democratic, that is not free, and that does not have the best interests of its people at heart," Rice said.

North Korea's nuclear capability was expected to be a major topic of Rice's talks with South Korean leaders on Sunday and Chinese officials on Monday.

Rice appealed to China, North Korea's closest ally, to use its leverage to bring the North back to disarmament talks.

The United States, Russia, Japan, South Korea and China began a joint diplomatic effort with North Korea last year aimed at persuading the country to give up its nuclear program.

But those six-nation talks, hosted by China, stalled in September, when the North Koreans pulled out and refused to return to the discussions. North Korea announced last month it has built a nuclear weapon.

Rice said Saturday in Tokyo, her last stop before Seoul, "We are committed to diplomacy, but I think it goes without saying that no one is going to be prepared to allow the North Koreans to just go down a road that threatens everyone."

The North Koreans have not responded to a U.S.-backed peacemaking proposal and have demanded an apology after Rice this year branded the country an "outpost of tyranny."

North Korea has said it wants nuclear weapons as a defense against a potential attack from U.S. and South Korean forces.