Chennai, July 5 (IANS): Superstars Rajinikanth and Vikram are most likely to join hands for the highly anticipated sequel to filmmaker S. Shankar's blockbuster "Enthiran". The pre-production work on the project is already underway.

"Rajinikanth sir is already on board. Vikram is quite excited about the project, but he's yet to sign on the dotted line," a source told IANS.

Since Vikram already has two projects in his kitty, he's taking time to take a call.

"For the next six months, he'll be busy shooting for two yet-untitled Tamil projects. With such a busy schedule, he's concerned how he's going to take out time for 'Enthiran 2'. Hence, the delay in signing the project," the source said.

Vikram has been reportedly offered the role of the antagonist in the film.

"It's not sure what role he'll be playing. It's one of the important characters, but it can't be said certainly whether he's playing the baddie," the source added.

The pre-production work started a few months ago on the project, which is going to be directed by Shankar.

Rajinikanth will start shooting for his next film with director Pa. Ranjith from August and as soon he completes it, he will take a short break and start work on "Enthiran 2".