President-elect Barack Obama announced in a written statement on Sunday that Pete Rouse, his Senate chief of staff, will serve as “senior adviser” in the White House.

Rouse, a powerful figure on Capitol Hill who had previously been chief of staff to former Senate Democratic leader Tom Daschle (S.D.), is a member of Obama’s most inner circle who got Obama up and running on Capitol Hill after he was elected in 2004 and assisted him in making his decision whether to run for president.

The senior adviser role in past administrations has been a relatively undefined but supremely powerful post, held by someone close to the president who is given license to dip into multiple issues and projects on behalf of the president while having almost unimpeded access to him. The incoming chief of staff, Rep. Rahm Emmanuel (D-Ill.), served in a similar role under President Bill Clinton.

Obama is beginning to round out his White House staff, but has yet to appoint any Cabinet members.

In an interview this morning on C-SPAN, Democratic Caucus Vice Chairman John Larson (Conn.) said Obama staffers will be meeting with Democratic officials on Capitol Hill the first week of December to discuss economic and national security issues. Larson is expected to be voted Caucus chairman later this week.

Obama also said he is tapping Mona Sutphen and Jim Messina to be his White House deputy chiefs of staff. Both are members of the transition team staff. Traditionally, one of the White House deputy chiefs of staff deals with management issues and the other with policy.

While the announcement did not specify their responsibilities, Sutphen has a long history of foreign policy experience while Messina’s expertise is in management. He is currently director of personnel for the transition and has served as chief of staff for Sens. Max Baucus (D-Mont.) and Byron Dorgan (D-N.D.) and Rep. Carolyn McCarthy (D-N.Y.).