The US has rejected linking a revival of the Iran nuclear deal with the closure of probes by the UN nuclear watchdog a day after Iran reopened the issue, a Western diplomat said.

Iran on Thursday sent its latest response to a European Union proposed text to revive the agreement known as the JCPOA.

Former US President Donald Trump abandoned the deal in 2018 and re-imposed US sanctions, prompting Iran to start breaching the deal's nuclear curbs and reviving US, Arab and Israeli fears it may be seeking an atomic bomb.

"There should not be any conditionality between re-implementation of the JCPOA and investigations related to Iran's legal obligations under the Non-proliferation Treaty," White House press secretary Karine Jean-Pierre said.

Jean-Pierre was alluding to investigations by the Vienna-based International Atomic Energy Agency (IAEA) into uranium traces found at three undeclared Iranian sites.

Resolution of the so-called safeguards investigations is critical to the UN agency, which seeks to ensure parties to the Nuclear Non-Proliferation Treaty are not secretly diverting nuclear material which they could use to make a weapon.

A senior US official on Aug. 23 said Iran had "basically dropped" some of the main obstacles to reviving the 2015 deal, including on the IAEA, but the issue seems to have been deferred.

A Western diplomat who spoke on condition of anonymity said on Friday Iran had reopened the issue in its latest response, which Washington characterized as “Not constructive”.

Iran's foreign minister this week said the IAEA should drop its "politically motivated probes" of Tehran's nuclear work.

Reporting by Reuters