While the Bush administration concentrates this week on the war in Iraq, fresh signs of success appear in its diplomatic course in dealing with North Korea. Pyongyang has invited experts from the United States, China and Russia to inspect the nuclear sites that it has agreed to shut down.

The inspection invitation was overshadowed by reports of a tense exchange in Sydney, Australia, between President Bush and President Roh Moo-hyun of South Korea over the 50-year absence of a peace treaty ending the Korean war. Mr. Roh pressed Mr. Bush on the matter, possibly for internal political reasons. Mr. Bush snapped back that it was up to North Korea’s president to get rid of his nuclear weapons before a peace treaty could be signed.

That, of course, goes to the heart of the agreement signed last February that sets forth a series of phased steps in which both the United States and North Korea will make concessions. The agreed end result will be a nuclear-free Korean peninsula and normalized political and economic relations. A formal end of the Korean war will be among the final steps.

The February agreement was remarkable, since it came after years of acrimony, in which President Bush said he “loathed” the North Korean president and listed North Korea with Iraq and Iran as an “axis of evil.” The North Korean leader reciprocated with equally harsh language. A group within the Bush administration had been pushing for an airstrike as a last resort to wipe out North Korea’s nuclear program.

Instead, Secretary of State Condoleezza Rice gave Ambassador Christopher Hill authority to pursue negotiations. Such talks had been criticized by hardliners, such as former U.S. Ambassador to the United Nations John Bolton, as sending “the wrong signal to proliferators around the world.”

It may not work at all. North Korea has often been erratic and unpredictable. On the U.S. side, some in the administration are still adamantly opposed to the diplomatic path.

Much will depend on this week’s scheduled international inspection tour. It must make a judgment on the effectiveness of North Korea’s claimed action to “disable” its acknowledged plant using plutonium as fuel. It may also check on the truth or falsity of a U.S. claim that North Korea also has been secretly using enriched uranium as an alternate method to build nuclear weapons.

The United States is treading new ground in relations with North Korea. So far, the effort is on track.