John Bolton (search), the State Department's top international security official, will leave the post in the second Bush administration and be replaced by an arms control specialist at the National Security Council (search), a senior U.S. official said Friday.

Bolton, who promoted programs to slow the spread of sophisticated weapons technology around the world, has served as undersecretary of state for arms control and international security in the four years of the first Bush administration.

A tough-minded Yale-educated lawyer, Bolton has been outspoken in warning of the proliferation of nuclear technology and programs to develop weapons of mass destruction in North Korea, Iran and elsewhere around the globe.

He took such a vehement stand against North Korea that the Pyongyang government refused to accept him as a member of the U.S. delegation in talks designed to halt North Korea's nuclear program.

Those negotiations have stalemated and no further rounds have been scheduled.

Jack Pritchard, who dealt with North Korea before leaving the State Department in 2003, said Bolton "played a disruptive role" in the implementation of President Bush's policy toward North Korea.

"He has undermined Secretary of State Powell's leadership and relationship with the president in the development of an effective policy toward North Korea," Pritchard said in an interview.

Also, Pritchard said, Bolton's public attacks on North Korean leader Kim Jong Il (search), while largely accurate, conveyed a tone contrary to the desires and direction of U.S. policy.

Balbina Hwang, of the conservative thinktank Heritage Foundation, said Bolton's outspoken criticism of North Korea was appropriate because it undercut the notion that the United States was trying to woo Pyongyang into multilateral discussions on dismantling its nuclear weapons.

"North Korea has to come to the bargaining table because they feel pressured to do so, not because they were enticed to do so or feel that they will be rewarded," she said.

North Korea did not take kindly to Bolton's broadsides, once calling him "human scum."

Bolton's replacement would be Robert G. Joseph (search), who worked closely with Condoleezza Rice (search), Bush's choice to take over as secretary of state, on proliferation policy, said the U.S. official who disclosed the pending appointment on condition of anonymity.

Joseph served in the administration of President George H.W. Bush, specializing on anti-ballistic missiles and arms talks with Moscow, and at the Pentagon in the Reagan administration. He has taught at Carleton College and the Fletcher School of Law and Diplomacy, and was educated at Chicago and Columbia universities.

Efforts to reach Bolton were unsuccessful. There was no word on whether he would be offered another post.

Meanwhile, an administration official said that Nicholas Burns, U.S. ambassador to NATO, is slated for the State Department's third-ranking position, under secretary for political affairs.

Burns, a career diplomat, has served as ambassador to Greece and as spokesman for former secretaries of state Warren Christopher and Madeleine Albright.