The US denied Iranian claims that a deal has been reached to unfreeze $7 billion in the Islamic Republic's overseas funds, Anadolu Agency reports.
An Iranian media report said the deal was part of an agreement to secure the release of Iranian-Americans detained in Iran.
State Department spokesman Ned Price acknowledged the existence of talks concerning the prisoners' release, saying they are running in parallel to ongoing nuclear negotiations and the US is approaching both talks "with the utmost urgency."
But Price maintained all US sanctions remain in place "until and unless we're able to achieve a mutual return to compliance with the" 2015 Joint Comprehensive Plan of Action (JCPOA).
"The fact is, unfortunately, we don't have any breakthrough to announce any information relating to our negotiations," he told reporters. "At this stage, neither of these negotiations has been successfully concluded."
Iran said Monday that by week's end it would receive part of its $7 billion in assets currently frozen by South Korea.
Foreign Ministry spokesman Saeed Khatibzadeh said in Tehran that the necessary framework for unblocking the assets has already been identified and agreed upon.
He said a high-level delegation from a regional country will be visiting Tehran this week to finalize the mechanism for unblocking what he called "significant assets," without mentioning South Korea by name.
Tehran has accused Seoul of freezing more than $7 billion in foreign exchange reserves under US pressure.
Iran has more than $100 billion in assets frozen in several countries, including South Korea, Iraq, Japan, Canada and others.
The funds were frozen soon after former President Donald Trump withdrew the US from the nuclear deal in 2018 and reimposed sanctions on Tehran.