LOS ANGELES (Reuters) - Punk rock band Green Day will perform as planned at the MTV Video Music Awards in Los Angeles on Thursday after a case of severe dehydration sent frontman Billie Joe Armstrong to the hospital and forced the cancellation of a weekend concert in Italy.

Bass player Mike Dirnt told MTV News on Thursday that Armstrong, whose illness had not been explained, came down with "heavy, heavy dehydration" in Italy but was recovering well on a regimen of "push-ups, prayers and vitamins".

"It was like severe dehydration, influenza, and it was just a really, really bad situation," Dirnt told MTV News in a break for rehearsals for the VMA award show.

"He woke up in the morning and it was bad. Let's put it this way, if you're in your hotel room and you're vomiting profusely, it's not fun. So what are you gonna do? It's hard to sing while you're puking," he added.

The band canceled a show in Bologna on Sunday but said they hoped to make their way back to the Italian city as soon as possible.

As for Thursday's performance at the annual MTV VMA show, "We're ready to rock, we're gonna be here, we're gonna have a good time," Dirnt told MTV News.

(Reporting By Jill Serjeant; Editing by Marguerita Choy)