WASHINGTON (AP) — Connecticut Sen. Joe Lieberman, the Democratic Party’s vice presidential candidate in 2000 and now an independent who is one of John McCain’s strongest supporters, will speak at the Republican National Convention, an official said.

Lieberman will deliver a speech when Republicans gather in St. Paul, Minn., to nominate McCain for president, a party official told The Associated Press on Wednesday. The official requested anonymity because a formal announcement had yet to be made, and Lieberman’s office declined to comment.

Lieberman, 66, caucuses with Senate Democrats, though has been a strong supporter of the Iraq war and is a staunch backer of McCain’s presidential bid, traveling often with the Arizona senator and campaigning on his behalf during the GOP primary in states like Florida that have large numbers of Jewish voters.

As he weighs potential running mates, McCain is believed to be seriously considering choosing Lieberman, whom he counts among his closest friends, for the GOP ticket. Lieberman’s convention speaking slot doesn’t indicate either way whether McCain ultimately will choose his friend for the No. 2 slot.

Republican officials say top McCain advisers have been reaching out to big donors and high-profile delegates in key states to gauge the impact of picking an abortion-rights supporter like Lieberman. Conservative activists, in turn, are waging an increasingly vocal campaign against the move, raising the prospect of acrimony at the convention.

There’s also lingering questions of whether Republican National Committee rules would allow someone who is not registered as a Republican to be the vice presidential nominee, or whether they would need to be changed — a process that could incite a right-flank revolt.

Some Republicans speculate that Lieberman’s name simply is being floated to make a Republican abortion-rights backer, former Pennsylvania Gov. Tom Ridge, seem more acceptable to conservatives. Ridge, too, is believed to be under serious consideration, along with former Massachusetts Gov. Mitt Romney and Minnesota Gov. Tim Pawlenty, both Republicans and abortion-rights opponents.

As Al Gore’s running mate in 2000, Lieberman became the first Jewish vice presidential nominee. His campaign for the Democratic presidential nomination in 2004 failed.

After a surprising loss to Ned Lamont in Connecticut’s 2006 Senate primary, Lieberman defied Democratic leaders and ran as an independent in the general election. Top Democrats backed Lamont, a political newcomer, and Lieberman won support from the GOP, including his friend McCain.

Lieberman tends to vote with Democrats on most issues and is a longtime supporter of abortion rights, a stance that would rankle conservatives if he were McCain’s running mate.

Not only has Lieberman campaigned for McCain, he has criticized Democratic candidate Barack Obama. Senate Democrats have been tolerant of his political straddling because he holds their slim political majority in his hands.

Lieberman departed Tuesday for a trip to the Republic of Georgia, Poland and the Ukraine. He is expected to return to Washington on Thursday night.

In 2004, former Sen. Zell Miller, a Georgia Democrat, praised President Bush and mocked the Democratic ticket as weak on defense in a speech at the GOP’s national convention.