U.S. President Joe Biden says he will not lift economic sanctions against Iran unless Tehran first cuts its uranium enrichment back to the level it agreed to in the 2015 international treaty aimed at restraining its development of nuclear weapons.

Biden has said he wants the U.S. to rejoin the nuclear treaty with Iran that former President Donald Trump withdrew the U.S. from.

But when asked directly in a CBS News interview that aired Sunday whether the U.S. would lift sanctions first to get Iran to return to negotiations, Biden replied simply, "No."

He nodded in agreement with CBS anchor Norah O'Donnell that Tehran must first stop enriching uranium at a higher level than allowed under the treaty.

The pact had allowed Iran to enrich uranium at a 3.67% concentration level. But since mid-2019, it had pushed enrichment to a 4.5% level, and then last month to 20% - a level it had achieved before the accord.

Experts say Tehran now has enough low-enriched uranium stockpiled for at least two nuclear weapons, if it chooses to pursue their manufacture. But Iranian officials, to the long skepticism of Western governments, has long maintained that its nuclear program is for peaceful purposes.

Iranian Supreme Leader Ayatollah Ali Khamenei said on state TV that if the United States wants "Iran to return to its commitments, the U.S. must lift all sanctions in practice, then we will do verification and see if the sanctions were lifted correctly, then we will return to our commitments."

Khamenei's televised remarks were his first since Biden's January 20 inauguration.

But in a CNN interview after Khamenei's remarks, Iranian Foreign Minister Mohammad Javad Zarif said that there was no precondition that Iran receive compensation from the United States for the cost of sanctions imposed by Washington before restoring the nuclear pact.