The White House says it is waiting for international experts to verify Iran's compliance with a deal to curb its nuclear program before Washington's possible suspension of economic sanctions on Tehran.
"We want to make sure they don't cut any corners," White House spokesman Josh Earnest told a January 15 briefing.
His comments came ahead of an announcement later in the day by the U.S. State Department, which said Secretary of State John Kerry would meet EU foreign-policy chief Federica Mogherini and Iranian Foreign Minister Mohammad Javad Zarif in Vienna the following day to discuss the nuclear deal.
"All parties have continued making steady progress towards Implementation Day of the [Joint Comprehensive Plan of Action Iran nuclear deal], which will ensure the exclusively peaceful nature of Iran's nuclear program," State Department spokesman Mark Toner said in a statement.
Reuters and AFP quoted unidentified diplomatic sources as saying that the UN's atomic watchdog, the International Atomic Energy Agency (IAEA), is likely to issue a report on January 16 confirming that Tehran has complied with the terms of the deal.
Earnest said that while the Islamic republic is making important progress in implementing the July deal with world powers, Iran will not get any sanctions relief until the IAEA has independently verified that it has completed all necessary steps under the agreement.
He added that there is ample reason to distrust Iran and that the IAEA's role in verifying compliance is not a mere "technicality."
"When this agreement was being negotiated, the important, independent work of the IAEA was considered to be much more than a technicality," Earnest said.
"We're going to continue to apply pressure on Iran," he added.
Earnest said that because the United States was in "ongoing communications" with the IAEA about its verification work, he did not anticipate that a U.S. review of its findings would result in a "significant delay in moving forward" with the deal.
Iran and the so-called P5+1 group of world powers -- Britain, China, France, Russia, and the United States, plus Germany -- reached the agreement in Vienna on July 14, 2015.
Tehran has long maintained that its nuclear program is for peaceful purposes, while the West has accused Iran of pursuing an atomic weapon.
Earlier in the week, U.S. officials said that "implementation day" for the deal could occur within days.
Tehran is set to receive billions of dollars in economic sanctions relief in exchange for curbs to its nuclear program spelled out in the agreement.