A speech by Lieberman, the Democratic vice presidential candidate in 2000, could bolster the case that the presumptive GOP nominee can reach across the aisle and boost McCain's standing among independent voters, The Hill reported Wednesday.

McCain hasn't asked Lieberman to speak at the September RNC event in St. Paul, Minn., Republicans close to the senator said. But if the McCain camp believes an appearance by Lieberman would help.

"If Sen. McCain, who I support so strongly, asked me to do it, if he thinks it will help him, I will," Lieberman told The Hill.

A Lieberman aide said even though there are no plans for the senator to deliver a speech at the convention, it was a "likely possibility" he would address the Republican audience in some manner.