By Joseph Ax and Nate Raymond

NEW YORK (Reuters) - Prosecutors are reconsidering a 50-year sentence for a convicted robber and drug dealer, after a judge on Wednesday suggested they call Attorney General Eric Holder to ask him whether it was fair to "punish" a man for rejecting a plea deal and opting for a trial.

Randy Washington, 27, the Bronx man who faced the lengthy term after turning down a 10-year plea deal and getting convicted at trial, had been scheduled for sentencing in New York federal court on Wednesday.

But the hearing was adjourned so prosecutors could rework a deal carrying a shorter sentence, after U.S. District Judge Richard Sullivan repeated his criticism that the 50-year mandatory minimum sentence appeared to "punish" Washington for going to trial.

Sullivan even suggested prosecutors call Holder himself to ask if their actions comport with his recent directive cautioning prosecutors against routinely using the threat of harsher sentences to induce defendants to plead guilty.

"He won't look with pride on what you're doing here today," Sullivan said.

The case has highlighted the debate over prosecutors' use of so-called sentencing enhancements following plea negotiations.

The Obama administration has pushed to reduce sentences for some offenders as crime rates have declined and the prison population has grown to unsustainable levels.

In September, Holder issued a memo advising prosecutors to avoid employing the prospect of longer mandatory minimum prison terms in plea talks.

Sullivan cited the memo Wednesday in criticizing the sentence for Washington, who was convicted of robbery, narcotics and related charges.

In July, Sullivan said the potential 50-year term was legal but "unnecessary and unjust" and in a rare move pushed Manhattan U.S. Attorney Preet Bharara's office to seek a reduced sentence.[ID:nL2N0RP1KV]

In response, prosecutors offered to drop a 10-year enhancement based on a prior felony conviction for Washington.

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They separately offered Washington a new 25-year deal, which Washington rejected as it included an appellate waiver, a provision Sullivan questioned on Wednesday.

"I'm not sure there's great consistency in the position that says, 'We agree that 50 years is too long, but it's too long only if you give up your appellate rights,'" he said.

After prosecutors consulted with Bharara himself, Assistant U.S. Attorney Telemachus Kasulis told Sullivan they would consider a 25-year deal without requiring Washington to waive all of his appellate rights.

Sentencing was rescheduled for Dec. 12. A Holder spokeswoman did not respond to a request for comment.

(Reporting by Joseph Ax and Nate Raymond; Editing by Noeleen Walder and David Gregorio)