The United States will not accept a nuclear-armed North Korea and is committed to defending neighboring South Korea and Japan, the nominee to be the State Department's top Asia envoy said Wednesday. Kurt Campbell, speaking at his Senate confirmation hearing to be the assistant secretary of state for East Asian affairs, said North Korea poses a “direct and reckless challenge” to the world. He was referring to Pyongyang's recent nuclear test, a series of missile launches, and threats against its neighbors. “If confirmed, I would use close bilateral and trilateral coordination with Tokyo and Seoul to make clear that neither the United States nor its allies will accept a nuclear North Korea,” Campbell said. “The United States is firm in its resolve to uphold its treaty commitments regarding the defense of its allies.” Campbell also said the United States was leaving open a door to North Korea to rejoin multilateral disarmament talks. Pyongyang in April quit the six-country process to abandon its nuclear weapons in exchange for energy aid and security guarantees. Campbell would replace Christopher Hill, an architect of the six-country agreement who was named by President Barack Obama to be the U.S. ambassador to Iraq. Campbell was a Pentagon official dealing with Asia under former President Bill Clinton. He founded the Center for a New American Security, a think tank focused on defense policy.