"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".