President Bush and Sen. John Kerry agreed in their debate Thursday that the United States must talk to North Korea (search) to resolve concerns over its nuclear activity, but they differed sharply over how to do it.

Bush defended his administration's participation in six-nation talks on North Korea's suspected nuclear weapons development, while Kerry said a bilateral track would bring more progress.

"I'm going to immediately set out to have bilateral talks with North Korea," said Kerry, who added that North Korea had acquired more weapons during Bush's term in office.

Bush responded that direct talks between Washington and Pyongyang (search) would undercut the six-party negotiations in Beijing and remove China (search) as a powerful influence on its communist neighbor.

"It's a big mistake to do that," Bush said.

The difference centers on the U.S. administration's view that involving other countries in talks with North Korea will put more pressure on the isolated country. China is a major source of fuel and other supplies to the North.

North Korea, however, believes the United States is its No. 1 enemy, and has preferred to negotiate directly with Washington to extract concessions and elevate its own status. It has said it is willing to meet U.S. concerns in exchange for economic aid and security guarantees.

The talks in Beijing, involving the United States, North and South Korea, China, Russia and Japan, have so far yielded little progress.

Another round scheduled for September never happened after North Korea refused to attend, apparently because of tension with Washington. Experts say North Korea might hope that a Kerry victory would soften U.S. policy.