President Hassan Rouhani pledged on Saturday to open Iran to the world and deliver freedoms its people have yearned for, throwing down a defiant challenge to his hardline opponents after securing a decisive re-election for a second term.

Rouhani, long known as a cautious and mild-mannered establishment insider, reinvented himself as a bold champion of reform during the election campaign, which culminated on Friday in victory with more than 57 percent of the vote. His main challenger, hardline judge Ebrahim Raisi, received 38 percent.

In his first televised speech after the result, Rouhani appeared to openly defy conservative judges by praising the spiritual leader of the reform camp, former President Mohammad Khatami. A court has banned quoting or naming Khatami on air.

"Our nation's message in the election was clear: Iran's nation chose the path of interaction with the world, away from violence and extremism," Rouhani said.

U.S. Secretary of State Rex Tillerson, whose country has had no diplomatic relations with Iran since 1980, said he hoped Rouhani would use his second term to end Tehran's ballistic missile program and what he called its network of terrorism.

Iran denies any involvement in terrorism and says its missile program, which U.S. President Donald Trump recently targeted with new sanctions, is purely for defense purposes.

Although the powers of the elected president are limited by those of unelected Supreme Leader Ayatollah Ali Khamenei who outranks him, the scale of Rouhani's victory gives the pro-reform camp its strongest mandate in at least 12 years to seek the sort of change that hardliners have thwarted for decades.

Rouhani's opponent Raisi, a protege of Khamenei, had united the conservative faction and had been tipped as a potential successor to the 77-year-old supreme leader. His defeat leaves the conservatives without an obvious flag bearer.

The re-election is likely to safeguard the nuclear agreement Rouhani's government reached with global powers in 2015, under which most international sanctions have been lifted in return for Iran curbing its nuclear program.

And it delivers a setback to the Revolutionary Guards (IRGC), the powerful security force which controls a vast industrial empire in Iran. They had thrown their support behind Raisi to safeguard their interests.