It is the Diamond League season debut for both Jamaicans, and Bolt acknowledged on Tuesday that he's "slightly nervous" for the first time in his career.
"That makes two of us, because it's pretty much our first real competition," Powell said yesterday.
"Every sprinter, when they're going to run their first competition, they're a bit nervous about seeing where they're at, or if they forgot how to run.
"I'm just going out to give my best. Just go all out and see what the results will be."
Since Powell set a world record of 9.74 seconds at Rieti, Italy, in 2007, Bolt has broken the mark three times, the last being a 9.58 at the 2009 world championships in Berlin. European champion Christophe Lemaitre, of France, is also in the field for the annual meet at the Stadio Olimpico.
"I want to keep up with them at the start so I don't get left behind, like last year," Lemaitre said. "In terms of a time, I want to try to run around 10.0 or less, if the conditions are there."
Lemaitre's personal best is a 9.97.
Powell held the world record for three years between June 2005 and May 2008, when Bolt became the world's fastest man.
Bolt has beaten Powell in eight of their nine meetings, with Powell's only win coming in Stockholm in 2008.
Never one to get too riled up, Powell answered courteously each time a reporter asked him about Bolt.
"Bolt is the man now, so there's definitely questions about him," Powell said, taking off his dark sunglasses as he sat down in front of a huge photo of Bolt. "I don't mind. I know what to say and I know how to answer to those questions."
Powell also said that Bolt's performances have pushed him "to work harder than you normally do."
Powell is running for the eighth time in Rome, while this marks Bolt's debut. Last year here, Powell won in 9.82 and Lemaitre edged fellow Frenchman Martial Mbandjock in a photo finish for second in 10.09.