"Ali Larijani was appointed secretary of the Supreme National Security Council in a decree by President Masoud Pezeshkian," official news agency IRNA reported.

Larijani, 68, who is seen as a moderate conservative in Iran, replaces Ali Akbar Ahmadian, a Revolutionary Guards general who was named to the position in May 2023.

His appointment comes after a 12-day war in June, launched by Israel and later joined by the United States, during which key Iranian nuclear and military sites were hit.

The security council is responsible for laying out Iran's defence and security strategy, but its decisions must be approved by the country's supreme leader, Ayatollah Ali Khamenei.

The secretary, as the most senior member of the council, oversees the implementation of its decisions.

A former member of the Islamic Revolutionary Guard Corps, Larijani has held several senior government positions over three decades.

Khamenei made him one of his advisers in May 2020.

The following year, Larijani's presidential run was blocked by a government vetting body despite him being considered a leading candidate.

Starting in 2005, Larijani had led Iran's nuclear policy but resigned after two years of negotiations with Western powers, citing "serious differences" with the president at the time, ultra-conservative Mahmoud Ahmadinejad.

As parliament speaker from 2008 to 2020, Larijani put his weight behind the 2015 nuclear agreement with world powers.

The son of a grand ayatollah, Larijani comes from an influential Shiite Muslim family with ties to the government, and holds a doctorate in philosophy.

Tehran and Washington had been engaged in negotiations aimed at reaching a new nuclear deal earlier this year, but the talks were derailed by the Israel-Iran war.

Israel said its offensive was aimed at preventing Iran from acquiring nuclear weapons, an ambition Tehran has consistently denied pursuing.