US President Joe Biden's administration said Wednesday that its "patience is not unlimited" with Iran as it renewed an offer for talks on its nuclear program.
The United States on February 18 offered to meet with Iran under the auspices of the European Union in a bid to revive a nuclear deal trashed by former president Donald Trump.
"This is an urgent challenge for us," State Department spokesman Ned Price said, referring to Iran's steps out of compliance with the deal in protest against Trump's sanctions.
"Our patience is not unlimited," Price told reporters.
"But we do believe, and the president has been clear on this," Price said, "that the most effective way to ensure Iran could never acquire a nuclear weapon was through diplomacy. That is what we are engaged in now."
The White House press secretary, Jen Psaki, separately said that the United States was still awaiting Iran's response to the European invitation for a meeting.
Iran publicly has insisted on its position that the United States needs to lift all sanctions before Tehran returns to compliance.
The Biden administration last week took symbolic steps including reversing Trump's widely dismissed stance that the United Nations had authorized new sanctions on Iran -- but has said that talks are the best way to resolve all issues.
Iran this week began limiting the International Atomic Energy Agency's access to sites and other information in response to the US refusal to lift sanctions immediately.
But in a compromise, Iran agreed to a temporary technical deal that IAEA chief Rafael Grossi said gives the watchdog "necessary degree of monitoring and verification work."