WASHINGTON (AP) - The Supreme Court has ruled that a man convicted of armed robbery may not withdraw a guilty plea even though the government reneged on a plea agreement, arguing for a longer sentence.

In a 7-2 decision Wednesday, the court upheld a 29-year prison term for James Benjamin Puckett, who pleaded guilty to armed bank robbery in Dallas, Texas.

A condition of the plea was that prosecutors would tell the sentencing judge that Puckett had accepted responsibility for his actions and should be eligible for a shorter sentence. The government agreed to recommend that Puckett be sentenced at the low end of the range of prison terms set out in federal sentencing guidelines.

But in between his plea and sentencing, Puckett was implicated in another crime. Prosecutors told the judge that Puckett should not get credit for accepting responsibility for his crime.

The trial judge could have shortened Puckett's sentence by roughly six years, but said he wouldn't because of Puckett's subsequent criminal activity.

Puckett raised the government's breach of the agreement on appeal, but the New Orleans-based 5th U.S. Circuit Court of Appeals ruled against him.

Hon. Antonin Scalia, writing for the high court, said that since Puckett "obviously did not cease his life of crime," giving him credit for accepting responsibility "would have been so ludicrous as itself to compromise the public reputation of judicial proceedings."

Hon. David Souter and Hon. John Paul Stevens dissented. "Puckett is entitled to relief because he and every other defendant who may make an agreement with the government is entitled to take the government at its word," Souter said.

The case is Puckett v. U.S., 07-9712.