U.S. President Barack Obama says his national security adviser, James Jones, will step down later this month. Jones will be replaced by his deputy, Tom Donilon.
In the White House Rose Garden, President Obama thanked his outgoing national security adviser, calling him a steady voice in the administration during a time of great change.
"He has led an unprecedented reform of our national security staff here at the White House," said President Obama. "Reflecting the new challenges of our time, he put new emphasis on cybersecurity, development and climate change, and made sure that homeland security is fully integrated into our efforts."
The president said General Jones had agreed to serve for two years when he accepted the post early last year, after a long career in the military.
Jones said he was proud of the progress he said the administration has made in improving America's relationships around the world.
"Where we are today in the global playing field, and how the United States is held in the esteem of the rest of the world, is an accomplishment that I frankly find astonishing in such a short period of time," said James Jones.
Jones is a retired Marine Corps general with 40 years in the service.
Donilon has never served in the military. He has had a career as a lawyer, political adviser and U.S. diplomatic official. He was the State Department's chief spokesman in the 1990's.
Mr. Obama says his deputy national security adviser has played a key role in many important decisions.
"Over the last two years, there is not a single critical national security issue that has not crossed Tom's desk," said Mr. Obama. "He has helped manage our national security team and the policymaking process, and won the respect and admiration of his colleagues in the White House and across the administration."
Tom Donilon was heavily involved in the process of shaping the Obama administration's policy in Afghanistan.
A recent book by journalist Bob Woodward quoted Defense Secretary Robert Gates as saying during that process that Donilon would be a "complete disaster" if promoted to national security adviser.
Gates said Friday he and Donilon work well together.
"I have thoroughly enjoyed working with General Jones, and I have and have had a very productive and very good working relationship with Tom Donilon, contrary to what you may have read, and I look forward to continue working with him," said Gates.
General Jones is the latest of several Obama aides to step down recently. Others have included White House chief of staff Rahm Emanuel and financial advisers Larry Summers, Christina Romer and Peter Orszag.