SEOUL (Reuters) - The recent nuclear deal with Iran showed that the United States can be flexible with a willing counterpart, including North Korea if it decides it wants talks on its nuclear program, a U.S. envoy said on Monday.

North Korea has said it was not interested in an Iran-like dialogue with the United States to give up its nuclear capabilities, which it said were an "essential deterrence" against hostile U.S. policy.

Despite that, Sydney Seiler, U.S. special envoy for now-defunct six-party talks on ending the North's nuclear program, said the United states left the door open to talks with the North when it is willing to end its diplomatic isolation.

"The Iran deal demonstrates the value and possibilities that negotiation bring," Seiler told reporters in the South Korean capital, Seoul.

"It demonstrates again our willingness, when we have a willing counterpart, and it demonstrates our flexibility when the DPRK makes a decision that it wants to take a different path," he said, referring to North Korea by the initials of its formal name, the Democratic People's Republic of Korea.

Seiler is on a trip to the region that will include stops in China and Japan, is the latest in a series of visits by U.S. nuclear envoys aimed at trying to jump start the North Korean talks which broke down in 2008.

North Korea has conducted three nuclear tests, the last in February 2013, and now calls itself a nuclear weapons state.

The United States and five world powers struck a historic deal with Iran this month that will limit Iran's nuclear capabilities in exchange for lifting U.S., EU and UN sanctions that have crippled its economy.

North Korea is also heavily sanctioned by the United States, European Union and the United Nations for procuring equipment related to its nuclear and ballistic missile programs.

News reports said the North has recently upgraded a missile platform and may be readying to launch a long-range missile around the time of a national anniversary in October.

(Reporting by James Pearson; Writing by Jack Kim; Editing by Robert Birsel)