Iran's main pro-reform opposition leaders plan to speak out from their confinement under house arrest this month to publicly back President Hassan Rouhani for re-election, aides say, helping win over voters disillusioned with the slow pace of change.

Axar.az reports citing to Reuters Rouhani was elected in a landslide in 2013 on promises to ease Iran's international isolation and open up society. He is standing for a second term against five other candidates, mostly prominent hardliners, on May 19, with a run-off a week later if no candidate wins more than 50 percent of votes cast in the first round.

In his first term, Rouhani expended his political capital pushing through a landmark agreement with global powers to limit Iran's nuclear program in return for the lifting of international financial sanctions.

But even his supporters acknowledge he has made comparatively little progress on his domestic agenda, after promising that Iranians should enjoy the same rights as other people around the world.

Some reformist critics say he neglected the cause of curbing the powers of the security forces and rolling back restrictions that govern how Iranians dress, behave, speak and assemble.