OTTAWA — Former Ontario premier David Peterson warned Wednesday that erstwhile NDP rival Bob Rae won't be welcome in the federal Liberal leadership race.

Rae would be a divisive force in a Liberal leadership race, said Peterson, who was driven from politics by his stunning 1990 election loss to Rae. "It's a dilemma for a tremendous number of people in the party," Peterson told The Canadian Press.

"Here's a guy, a lot of people went to war with him and now he wants to lead the army without even enlisting."

Rae is expected to formally join the race to succeed Paul Martin within a couple of weeks. He declined to respond to Peterson's comments Wednesday.

But Peterson, who's expected to back rookie MP Michael Ignatieff's candidacy, warned that Rae has "got some terrible burdens to overcome."

"One is his record and one is his loyalty."

Rae served one tumultuous term as Ontario's premier, infuriating both business and labour as he struggled with soaring deficits and a recession-ravaged economy. He was eventually defeated by Mike Harris's Conservatives in 1995.

Since then, the fluently bilingual Rae has rehabilitated his reputation and moderated his politics. He has been sought after at home and abroad to advise on complex issues, from Sri Lanka's peace process to the need for a public inquiry into the Air India tragedy.

Both Martin and former prime minister Jean Chretien tried unsuccessfully to woo Rae to run for the Liberals. He refused entreaties to run against federal NDP Leader Jack Layton in last winter's election and turned down the chance to run in another Toronto riding as well.

Rae finally took out a Liberal party membership this week. His brother, Power Corp. executive John Rae, headed up all of Chretien's successful campaigns and is well respected in the party but Peterson doubted the family connection is enough to overcome doubts about the onetime New Democrat's suitability for the top Liberal job.

Peterson insisted he doesn't hold any personal grudge against Rae but is simply being realistic about the reception he'll get from Liberal militants who've given blood for the party through good and bad times.

"It's so obvious. Everybody's talking about it . . . It's a helluva high hill to climb."

Party politics "is tribal and it's primordial and it's based on trust and affection and shared experiences," Peterson observed.

"Some people would say you just can't pick the cherries off the top."

On that score, he acknowledged that lack of history in the party will hurt two other prospective leadership candidates - Belinda Stronach and Scott Brison, both relatively recent defectors from the Tories.

"It does absolutely (hurt) but it doesn't hurt them as much because the sense is they've been sanitized at least by (running for the Liberals in) one election."

Peterson was the go-between who arranged Stronach's surprise defection to the Liberals last May, just in time to save Martin's minority government from defeat in a confidence vote.

"Let me be fair. Everybody in this race has some baggage," Peterson admitted. "One of the issues is who can shed that."

Still, Peterson suggested Rae's baggage will be harder to unload than most.

"It's not a bit of a problem. It's a huge problem."

Peterson had hoped to support former New Brunswick premier Frank McKenna. Since McKenna bowed out of the race, Peterson hasn't formally declared support for any other candidate but he acknowledged he's very impressed by Ignatieff, an acclaimed academic.