U.S. prosecutors lost a major terrorism case on Thursday, when a mistrial was declared in the case of six men accused of plotting to blow up Chicago's Sears Tower.

A seventh man was acquitted.

The mistrial was declared after a federal jury in Miami failed to reach a verdictfollowing nine days of deliberations. The jury of six men and six women twice sent notes to the presiding judge indicating they could not reach verdicts, but were told to keep trying.

After their third note, U.S. District Judge Joan Lenard declared the mistrial.

Federal prosecutor Richard Gregorie said the government will retry the six men next year.

The seventh man, Lyglenson Lemorin, will not face another trial. He buried his face in his hands whenhis acquittalwas announced.

All seven men had been charged with terrorism-related offences that could have carried sentences amounting to 70 years in jail.

The men, known as the "Liberty City Seven" because they allegedlyoperated out of a warehouse in Miami's bleak Liberty City section, were accused of forging an alliance to carry out bombings against the Sears Tower, which at 108 storeys is the tallest building in the United States.

The men were also accused of plotting to bomb the FBI's Miami office and other federal buildings.

Alleged leader accused of supporting al-Qaeda

The group's leader, Narseal Batiste,was alleged to havepledged allegiance to al-Qaeda during dealings with an FBI informant who was posing as an al-Qaeda member. Batiste allegedly told the informant of plans to acquire uniforms, machine-guns, explosives, radios, vehicles and cash to enable his group to carry out its plans.

The administration of U.S. President George W. Bush had used theLiberty CitySeven caseas an example of the government's success in breaking up terror plots following the Sept. 11, 2001, attacks on the United States.

Government officials had also said the case exemplifies the danger of homegrown terrorism. Five of the accused men are American citizens, while two are Haitian. All were said to be part of a radical black Muslim group.

"They were persons who, for whatever reason, came to view their home country as the enemy," Alberto Gonzales, the U.S. attorney generalat the time, said when the men were arrested in June 2006.

With files from the Associated Press