CHICAGO - Lawyers for former Illinois Gov. Rod Blagojevich have subpoenaed White House chief of staff Rahm Emanuel as a witness at his corruption trial, attorneys close to the case said.

The racketeering and fraud trial is due to begin Thursday with jury selection, after 18 months of skirmishing in the courts and the media. Blagojevich, who is accused of trying to sell President Obama's former Senate seat, has pleaded not guilty.

The attorneys spoke on condition of anonymity, saying the subpoena was not public. A White House spokesman did not immediately respond to a message seeking comment.

If Emanuel did take the witness stand, he might be asked about what effort, if any, the White House had made to get Blagojevich to appoint Obama friend Valerie Jarrett to the seat. Neither Emanuel nor Jarrett, who had been mentioned as a possible candidate for the seat but withdrew her name to instead become a White House adviser, is accused of any wrongdoing.

According to the indictment, Blagojevich ordered an associate to pressure Emanuel - then a Chicago congressman - to get his Hollywood-agent brother to raise funds. It says Blagojevich told the associate to threaten to withhold money for a school in Emanuel's district. But nothing in the indictment suggests that Emanuel was actually threatened.

Blagojevich and his brother, businessman Robert Blagojevich, have pleaded not guilty to charges that they schemed to profit from the governor's power to fill the Senate seat. They have also pleaded not guilty to plotting to join with his key advisers to mobilize the powers of his office to further a moneymaking racketeering scheme.

U.S. District Judge James B. Zagel turned down a request from Blagojevich's lawyers for a delay in the trial. Scores of potential jurors were already in the federal courthouse filling out questionnaires.

Blagojevich's lawyers said in a motion filed late Tuesday that they had been swamped by as many as nine million pages of documents, 270 hours of tapes, and summaries of interviews with more than 700 people, and had not had time to cope with the massive amount of preparation.

The judge said he planned to call in and question a maximum of 34 jurors every day until a jury is seated.