WASHINGTON—Come January, not everyone from the Bush administration will be out of office.

As President-elect Barack Obama prepares to take over, federal agencies have been reassigning Bush appointees to career jobs. And in one case, the Interior Department's top lawyer has converted six political posts into civil-service positions.

The switch at Interior could delay for months the Obama administration's ability to fill the positions, but does not change the number of political jobs at the agency the incoming administration can fill, White House and Interior officials said.

"The administration on day one...can change that back," said Tina Kreisher, a spokeswoman for the Interior Department, acknowledging "there would be a slight delay in moving people out of those positions."

Since March 17, according to data from the Office of Personnel Management, the Bush administration has filled 20 career jobs at numerous agencies with political appointees. These job transfers, common during transition periods, are known as "burrowing," since civil service jobs are more permanent than political positions, which usually change with a new president.

In an internal memo on Nov. 13, Interior's solicitor, David Bernhardt, announced that he was converting six political positions to civil service posts, a move he said would ensure "substantial tenures in those positions." Only one of those positions will be filled by a former political appointee who has been involved in some controversial environmental decisions.

But environmentalists say the last-minute switch will make Bush environmental policies difficult for Obama to change.

"What they have done is converted political slots to career slots to put Bush loyalists in career slots," said Robert Irvin, senior vice president for conservation programs at Defenders of Wildlife. "Potentially, they could have quite a bit of impact by making it difficult for the new administration to implement its policies on environmental issues."

The White House denied Tuesday the moves were made to extend its policies into the next administration.

"The White House has not encouraged noncareer appointees to seek career positions in order to further the president's policies," said White House press secretary Dana Perino. "The White House doesn't play a role in that career hiring process."

Perino said that while the Bush administration has had 20 conversions in the past year, the Clinton administration had 47. She said the jobs are advertised, and anyone can apply.

Earlier this month, the Interior Department placed two former political appointees who had been involved in controversial environmental decisions and already had career posts into new civil service jobs.