"The country's policy regarding interaction with JCPOA parties and the JCPOA itself has been clear," Ayatollah Ali Khamenei said in a televised speech, referring to the accord by its official name, the Joint Comprehensive Plan of Action.

It "entails that the Americans must lift the sanctions, all the sanctions, and then we will verify and if they are truly lifted, then we will return to our JCPOA commitments".

Khamenei stressed that lifting sanctions "on paper is not acceptable" and had to be implemented "in practice".

The deal was meant to provide Iran with international sanctions relief in exchange for limitations on its controversial nuclear programme.

But it has been on life-support ever since former US president Donald Trump withdrew from it in 2018 and reimposed sanctions as part of a "maximum pressure" campaign against Tehran.

Joe Biden, who defeated Trump at the ballot box in November, has signalled his readiness to revive the accord, but his administration insists Iran must first return to its nuclear commitments, most of which Tehran has suspended in response to US sanctions.

Tehran has insisted Washington make the first move by scrapping the sanctions.

"If they accept and implement the policy we have announced then everything will be fixed. And if they don't, things will continue as they are now, and it is not an issue," Khamenei said.

He also repeated Tehran's stand that "maximum pressure has failed" and warned if the Biden adminstration "wants to continue maximum pressure, they will fail as well".

- Call to 'manage' social media -

On upcoming presidential and municipal elections, Khamenei said intelligence services of Iran's "enemies", mainly the US and Israel, had been trying to utilise social media to discourage voters and "reduce participation".

"They either accuse those holding it, (saying) the elections have been rigged or whatever, or they accuse the respected Guardian Council," a vetting body, he said.

"Or they discourage the people, saying: 'Your vote has no impact, it will not help improve the situation, (so) why bother?'"

Voters are on June 18 to elect a successor to President Hassan Rouhani, who is in his final four-year term.

Under Iranian law, candidates must be vetted by the powerful Guardian Council watchdog before being allowed to run.

Voter turnout hit a historic low of less than 43 percent in 2020 parliamentary polls after thousands of reformist candidates were barred from running, leading to a conservative landslide.

Khamenei also said Iranian social media "must not be left to the enemy that they would conspire" against Iran, calling for them to be "managed".

His warning comes after a report in Israeli media that a "No to Islamic Republic of Iran" campaign was gaining traction on social media.

The hashtags #NoVote and NoToIslamicRepublicOfIran have spread on Twitter, in both Farsi and English.