TEHRAN — Iran’s president said Sunday that he might invoke a powerful but neglected tool in his fight with hard-liners, suggesting the possibility of organizing direct referendums that would bypass the institutions the conservatives control and give more of a voice to Iranian voters.

President Hassan Rouhani, speaking during a conference on the country’s economic problems, said that Iranians were entitled to have major issues put to a nationwide vote, as described in the 1979 Constitution.

“It will be good to, after 36 years, even for once, or even every 10 years if we implement this principle of the Constitution, and put important economic, social and cultural issues to a direct referendum instead of to the Parliament,” Mr. Rouhani said.

In the opaque world of Iranian politics his remarks are a clear warning to hard-liners, who control the Parliament, key decision-making councils, the state-run media, the security forces and the intelligence services, but who have a shrinking base of support in the country.