VILLEPINTE, France, May 1 (Reuters) - French far-right presidential candidate Marine Le Pen would back a Europe of co-operation between nations while her rival Emmanuel Macron wants to keep France in the "EU jail," Le Pen ally Nicolas Dupont-Aignan said on Monday.

"Electing Emmanuel Macron, a junior, immature and troubled version of Francois Hollande, would mean locking up France definitively in the EU jail," Dupont-Aignan, the leader of a small nationalist, right-wing party who struck an alliance with Le Pen last week, told an FN rally.

"What's at stake this Sunday, what's at stake in 2017, is saving France," he said, referring to the decisive May 7 run-off vote between Macron and Le Pen.

"This will only be possible by regaining our independence ... and building the only Europe that can work, the Europe of nations ... of cooperation on specific projects."

Le Pen has said that Dupont-Aignan would be her prime minister if she were elected as French president. (Reporting by Ingrid Melander; Editing by Sudip Kar-Gupta)