U.S. Secretary of State Mike Pompeo has accused Tehran of not fully cooperating with the International Atomic Energy Agency (IAEA), saying that Iran's behavior "raises questions about possible undeclared nuclear material or activities."
Pompeo tweeted on September 10 that Tehran's "lack of cooperation" with the United Nations nuclear watchdog "fits into Iran's 40-year pattern of lies."
"The world won't fall for it," Pompeo said. "We will deny the regime all paths to a nuclear weapon."
Pompeo's Twitter statement came as Washington continues attempts to get other countries to increase pressure on Iran ahead of the 2019 United Nations General Assembly session.
But shortly after he tweeted those remarks, Pompeo told reporters it was possible that President Donald Trump could meet with Iranian President Hassan Rohani "with no preconditions" on the sidelines of the UN gathering, which starts on September 23.
France has been trying to convince Trump to meet with Iranian leaders, raising expectations that Tehran's nuclear program and its nuclear deal with world powers will be a major agenda item at the UN session.
Criticism of Iran from Washington was prompted by a meeting of the IAEA board of governors on September 9, where IAEA acting Director-General Cornel Feruta said he had informed Iranian officials during a recent visit to Tehran about the importance of "full and timely" cooperation with UN nuclear inspectors.
It also comes after IAEA inspectors reportedly found traces of nuclear material at a warehouse identified by Israeli intelligence officials as an undeclared nuclear facility.
"I also stressed the need for Iran to respond promptly to agency questions related to the completeness of Iran's safeguards declarations," Feruta said.
A recent IAEA report suggests Tehran has not been as forthcoming as hoped when responding to questions from IAEA inspectors.
Amid the questions raised about the warehouse, Iran has announced that plans to use more advanced centrifuges than allowed under its nuclear deal with world powers.
The IAEA has confirmed the installation of new centrifuges and said they had been prepared for testing.
Iran has already surpassed the limits set in the 2015 nuclear accord about enrichment purity and stockpiles of enriched uranium.
Trump withdrew the United States from the nuclear deal in 2018 and has reimposed crippling economic sanctions against Tehran. Washington also has been pressuring other countries to follow suit.
But French President Emmanuel Macron has sought to salvage the 2015 nuclear deal by creating a $15 billion line of credit for Iran in order to entice officials in Tehran to continue honoring Iran's obligations under the accord.
Macron has also been seeking to arrange a meeting between Trump and Rohani -- possibly at the upcoming UN gathering in New York.
On September 9, Trump told reporters that a meeting with Rohani "could happen."
"No problem with meeting," Trump said. "Iran should straighten out, because frankly they are in a very bad position right now and they should straighten it out because they could straighten it out very easy."