Chicago, Illinois (CNN) -- Lawyers for Rod Blagojevich filed a motion Thursday seeking to subpoena President Obama to testify in the corruption case against the former Illinois governor.
The 10-page motion contends that Obama must have information in the case because the charges against Blagojevich involve alleged deal-making to fill the U.S. Senate seat vacated by Obama when he became president.
"The defense understands that the President of the United States of America is not a routine witness and would not request his appearance if it did not think he was critical to the liberty of Rod Blagojevich," the motion says.
According to the motion, Obama's public assertion that he had no involvement in talks about filling his Senate seat contradicts information from another witness in the case.
In addition, the motion says that Tony Rezko, a political fundraiser convicted of fraud charges who has links to Obama, is a government witness in the case and that Obama can offer testimony about him.
Blagojevich, who faces racketeering charges, held a defiant news conference this week in which he called his accusers "liars" and "cowards" and directly challenged U.S. Attorney Patrick Fitzgerald, who is heading the prosecution. Blagojevich accused federal authorities of trying to keep some of the tapes FBI agents made of his phone conversations from being heard by a jury.
U.S. District Court Judge James Zagal said Wednesday that he would decide which of more than 500 hours of tapes would be played for the jury. At a preliminary hearing, Zagal gave the defense until May 14 to tell the court which tapes it wants played, warning, "I will not have the time of these jurors needlessly consumed."
During his news conference Tuesday, Blagojevich repeated that he was innocent and that the tapes of his conversations would prove it.
"It is because there is a smoking gun in those tapes, and the smoking gun is that the government is covering up the big lie Mr. Fitzgerald gave to the world when he had me arrested," Blagojevich said.
Authorities have said that Blagojevich and his inner circle engaged in a near-constant conspiracy of extortion and kickbacks after his 2002 election. The accusations also contend that tens of thousands of dollars in unearned commissions and unnecessary retainer fees were diverted to Blagojevich's wife after he and his co-conspirators learned that they were being investigated.
Blagojevich, a two-term Democrat, was impeached and removed from office in January 2009 amid accusations that he had attempted to sell the U.S. Senate seat that had been occupied by Obama. The former governor was arrested the month before on federal corruption charges that included wire fraud, mail fraud and solicitation of bribery.