CHICAGO - President-elect Barack Obama says he will resign from the U.S. Senate, effective Sunday.
In a statement, the Illinois senator called his four-year term "one of the highest honours and privileges" of his life.
He says the people of Illinois will stay with him as he leaves the Senate to begin "the hard task of fulfilling the simple hopes and common dreams of all Americans as our nation's next president."
The move was expected.
Obama won the presidency last week over Republican John McCain.
Under state law, Democratic Gov. Rod Blagojevich will name Obama's replacement for the remaining two years of his term.
Blagojevich has said he expects to make a decision by year's end, and had ruled out appointing himself. Obama is the only black senator.
Congress is scheduled to meet in a special session next week.
Potential candidates to replace Obama are Representative Jesse Jackson Jr., Representative Jan Schakowsky, Illinois Senate president Emil Jones and Illinois Attorney General Lisa Madigan.
