Raisi takes over from moderate Hassan Rouhani, whose landmark achievement during his two-term presidency was the 2015 nuclear agreement between the Islamic republic and six world powers.

Iran has been grappling with a deep economic and social crisis following former US president Donald Trump's decision to unilaterally withdraw Washington from the nuclear deal in 2018 and impose crushing sanctions.

"Sanctions against the nation of Iran must be lifted. We will support any diplomatic plans that will realise this goal," he said as he was sworn in during a televised ceremony.

But "the policy of pressure and sanctions will not cause the nation of Iran to back down from following up on its legal rights," he said, while reiterating Tehran's official position of pursuing solely "peaceful" nuclear technology.

The former judiciary chief officially began his four-year mandate on Tuesday when he was inaugurated by supreme leader Ayatollah Ali Khamenei.

On Thursday, he was sworn in before Iran's parliament, to which he will present his cabinet list early next week, state television reported.

Six rounds of nuclear talks between Iran and world powers were held in Vienna between April and June in an attempt to revive the accord. The last round concluded on June 20, with no date set for another.

In mid-July, Rouhani said he hoped his successor could clinch a deal to lift US sanctions and conclude nuclear talks.

Raisi also emphasised that one of his administration's main foreign policy priorities will be improving relations with regional countries.

"I extend the hand of friendship and brotherhood to all countries in the region, especially our neighbours," he said.

He also noted that Iran's regional "capabilities support the peace of security of countries" and would only be used "against the threats of oppressive powers."

Raisi had previously said there are "no obstacles" to restoring ties with Saudi Arabia, a US ally and the Islamic republic's rival in the Middle East.

Tehran and Riyadh have been engaged in talks hosted by Baghdad since April with the aim of improving relations.

Ties between the regional rivals were cut in 2016 after Iranian protesters attacked Saudi diplomatic missions after a revered Shiite cleric was executed in the kingdom.