The 11th Circuit Court of Appeals was set to hear arguments Wednesday over the conspiracy charge that was dismissed in August by a judge who ruled it was essentially the same as two other terrorism-support counts against Padilla and two co-defendants.
The three men are charged with being part of a North American cell that provided cash, supplies and recruits to Islamic extremists around the globe.
Federal prosecutors in November asked the 11th Circuit to reinstate the charge of conspiracy to "murder, kidnap and maim persons in a foreign country." They argue that the charge against Padilla was dropped in error, saying U.S. District Judge Marcia Cooke used the wrong legal analysis to dismiss the count.
A Jan. 22 trial date in the terrorism case is in jeopardy, as Cooke has said she will not allow the trial to go forward until the question before the 11th Circuit is settled.
Also, federal prosecutors asked the court Monday to reconsider its deadline for completing mental examinations to determine if Padilla is competent to stand trial.
Cooke last week gave prisons officials until Friday to complete the examinations, which she insisted be finished before his trial date so she can rule on a number of other outstanding issues, including Padilla's claim that the case should be dismissed because he was tortured in military custody — an allegation the government denies.
Padilla was arrested in 2002 at Chicago's O'Hare International Airport and originally accused of plotting to detonate a radioactive "dirty bomb" in a U.S. city.
President Bush designated him an enemy combatant, and the 36-year-old U.S. citizen was held without criminal charge at a Navy brig in South Carolina for 3 1/2 years, until he was added to a Miami terrorism-support case in late 2005.
He was added to that case amid a legal clash over the president's wartime detention powers. The dirty bomb allegations are not mentioned in the Miami indictment.
Co-defendants Adham Amin Hassoun and Kifah Wael Jayyousi are in custody overseas. All three have pleaded not guilty.