A prison manifesto by slain rap legend Tupac Shakur, dubbed as his letter to black men, is going up for sale.

MomentsInTime.com, a California-based memorabilia company, said it was selling the letter for $225,000.

Shakur spent nine months in a New York state prison in 1995 for a rape conviction. The rapper, who insisted he was innocent, used the time behind bars to read books on political philosophy.

In the handwritten letter to Nina Bhadreshwar, a British writer who came to Los Angeles to work for gangsta rap label Death Row Records, Shakur asked her to spread his "advice to young black men in America."

Shakur described racial abuse by the guards at the prison and offered a message of empowerment.

"I want all my homiez 2 realize there is another level," he wrote.

"It takes heart and courage 2 stand alone(,) face the demons and make a change!

"We are powerful people but not unless we have power and if we all die we have nothing," he wrote.

Gary Zimet, owner of MomentsInTime.com, said that Bhadreshwar had earlier sold the letter and that he bought it from the most recent owner, who would remain anonymous.

"It's an iconic letter," Zimet told AFP.

The $225,000 sale is the fixed price for the first buyer, he said.

When Shakur was in prison, his label released his third studio album, "Me Against the World," which marked the first time an incarcerated artist topped the US chart.

Less than a year after leaving prison, the 25-year-old Shakur was shot dead in Las Vegas in an assassination that remains murky.

Shakur is widely considered one of hip-hop's canonical artists, with a strong influence even on rappers who came of age after his death.

Interest in Shakur is especially strong ahead of next year's 20th anniversary of his killing.

Earlier this year, the Grammy Museum in Los Angeles opened an exhibit in cooperation with Shakur's estate that features his handwritten lyrics and other memorabilia.