A federal jury in Florida has cleared a man accused of plotting terrorist attacks in the United States, but said it was unable to agree on a verdict for six other defendants.

A judge in Miami declared a mistrial for the six other men, which leaves open the possibility that prosecutors can seek another trial.

The seven defendants were accused of plotting to join forces with al-Qaida and blow up FBI offices and topple the tallest building in the United States, the Sears Tower in Chicago.

Defense lawyers contended the alleged plot was mainly driven by FBI informants who persuaded the men to plan attacks. The defendants said they invented their terror plan in an effort to get cash from the informants, who said they had links to al-Qaida.

The federal government hailed the group's arrest last year as a major crackdown on home-grown terrorists. Prosecutors said no attack was imminent, but that the men's plans were more "aspirational" than "operational."

The defendants, who had been charged with terrorism-related conspiracy, were known as the Liberty City Seven, a name taken from the poor neighborhood of Miami where they met.

The 12-member jury met for more than a week before reporting Friday that it could agree only on acquittal for one of the seven defendants.

Some information for this report was provided by AFP, AP and Reuters.