For more than 15 years, the prevailing sentiment was that the only way former Van Halen singers David Lee Roth and Sammy Hagar would share a stage would be at a ceremony when receiving a major industr

For more than 15 years, the prevailing sentiment was that the only way former Van Halen singers David Lee Roth and Sammy Hagar would share a stage would be at a ceremony when receiving a major industry accolade for the band. But despite their publicized acrimony, the two frontmen shocked fans with the announcement of their co-headlining Song for Song: The Heavyweight Champs of Rock'N'Roll tour, which kicks off Wednesday (May 29) in Cuyahoga Falls, Ohio.

"Every time I did an interview last year, the rumor was [Van Halen] couldn't work with Dave anymore and now they were going to call me again," Hagar tells Billboard.com. "Some of their camp had called me and [Van Halen bassist] Michael Anthony had been working with me a little bit on a side project. Mikey would be saying, 'I don't know, Ed and Al (Van Halen) keep asking where is Sam's head at?' And I'm going, 'My head is the same place it's always been!'"

"The only way I would be interested is if we [both Roth and Hagar] do it all together because that would really be great for the fans and they're the ones who have been getting screwed all of these years," he continues. "So Dave called and said, 'They can't get it together. I can't get it together. Let's you and I do it,' and I said, 'right on.'"

The tour will find Hagar and Roth alternating opening and closing duties, with each playing a 90-minute set. Roth will fill his stage time entirely with Van Halen material, while Hagar plans on spanning his whole career, which essentially is no different than a normal solo show with his backing band, the Waboritas. "I usually play two-and-a-half hours, so I've taken an hour out of my set and I didn't take any Van Halen out," he says. In a unique twist, Anthony is expected to join Hagar's band for various shows, including the tour opener.

There's no disguising the rivalry that exists between Roth and Hagar, who will finally have a venue in which to exhibit their talents head-to-head. However, there's a certain degree of instability associated with Roth and his career. Diamond Dave's last major amphitheater tour came over 10 years ago in support of his 1991 release "A Little Ain't Enough." Considering Hagar must have heard stories while in Van Halen about their erstwhile singer, does he have any concerns about Roth's behavior?

"Of course, the few times I've been around him, he's definitely on the edge of going one way or another," Hagar admits. "I don't think he's quite as stable and consistent a human being or a performer as I am and I think he could easily do something. I'm worried about it because it's not going to change my life but I think it would really hurt the fans and the credibility of this tour if he pulled out for some reason."

"I'm telling you right now, if he does that to me ... first of all, I will go on anyway and I'll play for two-and-a-half hours," Hagar adds. "I'll play every old Van Halen song I know. I would call up Michael Anthony. I would call up Eddie Van Halen and say, 'Eddie, here's a million dollars, get your ass out here and play a couple of nights with me because Dave pulled out.' I would go that far with it if he pulled out. I will ruin him if he does that to the fans. It would be a horrible thing."

Depending on ticket sales (which are quite healthy so far) and how well Roth and Hagar get along, the tour may expand to a second leg. Asked what fans can expect when the tour opens next week, Hagar proclaims, "things could get ugly right out of the gate."

In other Hagar news, he recently finished recording a new album, tentatively titled "Sammy Hagar and Waboritas: Not For Sale" and slated for release in September. His Project Us side project with Anthony and Journey guitarist Neal Schon and drummer Dean Castronovo will also record an album, with an eye on a spring release and summer tour to follow.

Here are the Song for Song: The Heavyweight Champs of Rock and Roll tour dates:

May 29: Cuyahoga Falls, Ohio (Blossom Music Center)
May 31: Clarkston, Mich. (DTE Energy Music Theatre)
June 1: Tinley Park, Ill. (Tweeter Center)
June 2: Noblesville, Ind. (Verizon Wireless Music Center)
June 4: Cincinnati (Riverbend Music Center)
June 6: Bonner Springs, Kan. (Sandstone Amphitheatre)
June 7: Maryland Heights, Mo. (UMB Bank Pavilion)
June 8: East Troy, Wis. (Alpine Valley)
June 10: Peoria, Ill. (Peoria Civic Center)
June 11: Columbus, Ohio (Polaris Amphitheatre)
June 14: San Antonio, Texas (Verizon Wireless Amphitheatre)
June 15: Dallas (Smirnoff Music Centre)
June 16: Houston (C.W. Mitchell Pavilion)
June 18: Albuquerque, N.M. (Journal Pavilion)
June 19: Denver (Fiddler's Green)
June 21: Phoenix (Cricket Pavilion)
June 22: Devore, Calif. (Glen Helen Blockbuster Pavilion)
June 24-25: Hollywood, Calif. (Universal Amphitheatre)
June 27: Fresno, Calif. (Selland Arena)
June 29: George, Wash. (the Gorge)