The United States said Wednesday it would hold rare direct talks with North Korea next week on ending the authoritarian state's nuclear program and announced it was replacing its chief envoy.

The State Department said that US and North Korean officials will meet Monday and Tuesday in Geneva, following up on talks in July in New York, but that it was premature to consider a resumption of full-fledged negotiations.

"What we want to see is a seriousness of purpose," State Department spokesman Mark Toner said, calling for "firm signs" from North Korea that it will adhere to a 2005 six-nation agreement on denuclearization.

"We're not going, as we have said many times, to reward North Korea just for returning to the table or give them anything new for actions they've agreed to take," Toner told reporters.

Another US official said that the United States decided to hold talks not because of any new signals from North Korea but out of concern that the absence of dialogue could lead the Pyongyang regime to make "miscalculations."

"As we have seen in the past, sometimes when engagement is broken off, it causes them to lash out in dangerous and unsettling ways," the senior official said on condition of anonymity.

North Korea last year shelled a border island, killing four, and was accused of sinking a warship, killing 46 sailors. Ailing leader Kim Jong-Il is expected to hand power next year to his little-known youngest son, Kim Jong-Un.

The State Department said Stephen Bosworth was stepping down as the US coordinator on North Korea policy and would be replaced by career diplomat Glyn Davies. The two men will head together to Geneva.

Bosworth, 71, has served as ambassador to three countries including South Korea during a career spanning five decades but considered his latest job part-time. He spends much of his time in the Boston area or overseas as dean of the Fletcher School of Law and Diplomacy at Tufts University.

Toner described Bosworth's resignation as a personal decision and said it did not indicate any shift on North Korea, which along with its main ally China has pushed for the resumption of six-nation talks which also involve South Korea, Russia and Japan.

"This is a change in personnel, not a change in policy," Toner said.

"He has been in this job for nearly three years and he does have significant responsibilities in his job at the Fletcher School at Tufts University, so I think he wanted to focus on that," Toner said.

Davies now serves as the US representative to the International Atomic Energy Agency in Vienna and has previously held senior State Department positions including deputy spokesman.

Analyst L. Gordon Flake said that the appointment of Davies -- a non-proliferation expert who unlike Bosworth does not have direct experience on North Korea -- showed the administration's focus on the nuclear issue.

"Putting non-political professionals in these positions doesn't bespeak of grandiose, Hail Mary plans on North Korea. This is a careful, coordinated and measured approach done in consultation with our allies South Korea and Japan," said Flake, executive director of the Mansfield Foundation.

President Barack Obama has made dialogue a priority in his foreign policy but North Korea until recently was a notable exception, with his administration furious over provocations.

The United States is also holding talks this week with North Korea in Bangkok on resuming searches for the remains of thousands of Americans missing from the 1950-53 Korean War.

Victor Cha, a senior adviser on North Korea to former president George W. Bush, said that dialogue can help ease tensions, even if a breakthrough is unlikely.

"North Korea leaves you only with bad and worse options. Avoiding dialogue only promises a runaway nuclear program and more provocations," sad Cha, now a scholar at the Center for Strategic and International Studies and Georgetown University.

"Dialogue may not get denuclearization, but it does help to manage the situation, avert a crisis... and possibly offer small victories in freezing elements of the program," he said.

"It's not great, but it may be all we can hope for," he said.

The State Department also announced that Clifford Hart, another career diplomat, would serve under Davies as envoy to the moribund six-way talks. He replaces Sung Kim, who was named ambassador to South Korea.