US Attorney Patrick Fitzgerald said he needed more time to complete an investigation into allegations that Illinois Governor Rod Blagojevich conspired to profit from his powers to appoint Mr Obama's replacement.

Mr Fitzgerald asked a federal judge to give him until April 7 to seek an indictment from a grand jury so his team would have time to pour through thousands of conversations intercepted by FBI wiretaps and interview witnesses who have come forward in the wake of Blagojevich's Dec 9 arrest.

He also indicated that more people could eventually be charged in the case which accuses Blagojevich and his chief of staff of engaging in a years-long pattern of 'pay-to-play' politics in which he traded state contracts for campaign contributions.

While Mr Obama is not accused of any wrongdoing, the scandal has been an unwelcome distraction as he prepares to take office on Jan 20.

Blagojevich has refused to resign in the wake of his arrest on bribery and fraud charges and defied Democratic party leaders on Tuesday by appointing a prominent African-American statesman to the seat.

Blagojevich, who has vehemently proclaimed his innocence and said he 'can't wait' to clear his name in court, did not object to the prosecutor's request for a delay, according to the motion filed on Wednesday.

Should a grand jury determine that there is sufficient evidence to support the fraud and bribery charges it will likely be months or possibly years before the case goes to trial. -- AFP