U.S. Secretary of State Antony Blinken said on Tuesday it was up to Iran to engage to resolve a deadlock over its nuclear programme, and accused it of enabling Russian aggression in Ukraine.
Blinken, who was visiting Athens, said the United States was committed, together with Israel, to ensuring that Tehran "never acquire a nuclear weapon".
"That's not exactly news. The president (Joe Biden) has been very clear that every option is on the table to do that," Blinken told a news conference alongside his Greek counterpart, Nikos Dendias.
A 2015 agreement limited Iran's uranium enrichment programme to make it harder for Tehran to develop nuclear arms, in return for international sanctions being lifted. Iran consistently denies harbouring any nuclear weapon ambitions.
Biden's administration had been trying to resurrect the 2015 agreement, the Joint Comprehensive Plan of Action (JCPOA), which was abandoned by Biden's predecessor Donald Trump in 2018, but talks deadlocked in September.
Blinken accused Tehran of failing to engage and said the JCPOA was not on the table now.
"We continue to believe that, with regard to the nuclear programme, the most effective, sustainable way to deal with the challenge it poses is through diplomacy. But in this moment, those efforts are on the backburner because Iran is simply not engaged in a meaningful way," Blinken said.
"A lot depends on what Iran says and does and whether or not it engages."
Blinken added: "In the meantime, of course, we've seen provision by Iran of drones to Russia to enable its aggression in Ukraine."
He called the invasion a "strategic failure in every way" for Russian President Vladimir Putin.
(Reporting by Athens bureau; Writing by Michele Kambas; Editing by Kevin Liffey)