Biden made the comments as the two sat down for their first face-to-face meeting since Bennett was sworn-in as prime minister in June.

"We're putting diplomacy first and seeing where that takes us," Biden said during an Oval Office meeting on Friday that was delayed by the suicide bomb attack in Afghanistan. "But if diplomacy fails, we're ready to turn to other options."

Asked what other options Biden might be mulling, White House press secretary Jen Psaki declined to comment.

Bennett arrived at the White House aiming to dissuade Biden from returning to the Iran nuclear deal that was brokered during the Obama administration and later scrapped by President Donald Trump.

Since the US withdrawal from the deal in 2018, Tehran over time has abandoned every limitation the accord imposed on its nuclear enrichment. The country now enriches a small amount of uranium up to 63 per cent, a short step from weapons-grade levels, compared with 3.67 per cent under the deal.

It also spins far more advanced centrifuges and more of them than were allowed under the accord, worrying nuclear nonproliferation experts even though Tehran insists its program is peaceful.

Bennett expressed satisfaction that the two leaders were in sync on the notion that Iran should never be allowed to have a nuclear weapon.

"Iran is the world's number one exporter of terror, instability, and human rights violations," Bennett said. "And as we sit here right now the Iranians are spinning their centrifuges in Natanz and Fordo. And we got to stop it, and we both agree."

The meeting, originally scheduled for Thursday, was postponed for one day as Biden focused his attention on dealing with the aftermath of a suicide bomb attack at the Kabul airport that killed 13 US troops.

"These very days illustrate what the world would look like if a radical Islamic regime acquired a nuclear weapon," Bennett said. "That marriage would be a nuclear nightmare for the entire world."

Australian Associated Press