US Secretary of State Antony Blinken on Sunday said the United States has not seen yet whether Iran will do what it must to come into compliance with its nuclear commitments in order to have sanctions removed.
Iran President Hassan Rouhani last week said the United States was ready to lift trade sanction, although a senior Iranian official contradicted him, and European diplomats said very difficult issues remained.
Indirect talks have been underway in Vienna as the Biden administration seeks a path forward with Iran, including how Tehran can resume compliance with the 2105 nuclear deal with world powers.
"Iran, I think, knows what it needs to do to come back into compliance on the nuclear side, and what we haven't yet seen is whether Iran is ready and willing to make a decision to do what it has to do. That's the test and we don't yet have an answer," Blinken told ABC News' "This Week With George Stephanopoulos" program.
With a fifth round of discussions ahead, Blinken said, "the first thing that we need to do is put the nuclear problem back in the box." The talks, he added, helped clarify what both sides needed to do to move forward.
The United States abandoned the international pact in 2018 under former Republican US President Donald Trump, who reimposed sanctions on Iran's oil, banking and shipping sectors.
Democratic President Joe Biden, who succeeded Trump in January, has said he believes Iran is seriously engaging in talks but that it remained unclear what steps Tehran would actually take to comply with the deal, cemented when Biden was vice president under former President Barack Obama.