The United States, which has for two months been holding indirect talks with Iran on the future of the tattered nuclear deal, said Monday it was not even sure if Tehran really wanted to come back into compliance.
"We've been engaged in indirect conversations, as you know, for the last couple of months, and it remains unclear whether Iran is willing and prepared to do what it needs to do to come back into compliance," Secretary of State Antony Blinken told the House Foreign Affairs Committee.
"We're still testing that proposition," Blinken said.
Blinken also said that the breakout time for Iran to assemble a nuclear bomb could be reduced to just weeks if Tehran keeps violating the terms of the original 2015 nuclear accord that former U.S. president Donald Trump pulled out of in 2018, claiming that it did not do enough to prevent the Islamic republic from building a nuclear weapon.
Trump tightened sanctions on Tehran, and the Iranian authorities responded by loosening restrictions on their nuclear program imposed by the deal.
U.S. President Joe Biden has said he would rejoin the agreement if Iran lives up to its end of the bargain.
The two sides have been negotiating in Vienna since April through their partners in the multilateral agreement -- Britain, China, France, Germany and Russia.
The talks are scheduled to resume later this week in the Austrian capital.
"We're not even at the stage of returning to compliance for compliance," Blinken said. "We don't know if that's actually going to happen."
Earlier on Monday, Rafael Grossi, the head of the International Atomic Energy Agency (IAEA), said that Tehran had failed to provide answers for uranium found at former undeclared sites.
"After many months, Iran has not provided the necessary explanation for the presence of the nuclear material particles at any of the three locations where the agency has conducted complementary accesses," Grossi told the IAEA's board of governors.