US State Department spokesman Ned Price said on Monday that the United States will not impose a deadline on a seventh round of talks with Iran to revive the 2015 nuclear deal.
He noted that Tehran can determine when talks will resume.
"We're not imposing a deadline on these talks, but ... we are conscious that as time proceeds Iran's nuclear advances will have a bearing on our view of ultimately returning to the JCPOA," Price said, using the formal name of the accord, according to Reuters.
Iran has gradually scaled back its compliance with the 2015 deal in response to former US President Donald Trump’s withdrawal from the agreement, but has been holding indirect talks with the US on a return to the agreement.
Iran has insisted on a removal of all sanctions imposed on it, while the Biden administration has insisted that some will remain if they were imposed over other concerns, including human rights and Iran's support for extremist movements.
US Secretary of State Antony Blinken warned recently that time was running out to return to the 2015 nuclear deal.
"There will come a point, yes, where it will be very hard to return back to the standards set by the JCPOA," Blinken told reporters.
"We haven't reached that point -- I can't put a date on it -- but it's something that we're conscious of," he added.
German Foreign Minister Heiko Maas last week expressed confidence that a deal to save the 2015 nuclear accord with Iran would be reached "in the coming weeks".