The United States used intermediaries at the United Nations last month to attempt to make contact, Foreign Minister Hossein Amirabdollahian told state television.
Iran has been unable to obtain tens of billions of dollars of its assets in foreign banks, mainly from exports of oil and gas, due to U.S. sanctions on its banking and energy sectors.
"The Americans tried to contact us through different channels (at the U.N. General Assembly) in New York, and I told the mediators if America's intentions are serious then a serious indication was needed ... by releasing at least $10 billion of blocked money," the minister said.
"They are not willing to free $10 billion belonging to the Iranian nation so that we can say that the Americans once in the past several decades considered the interests of the Iranian nation," Amirabdollahian said.
Amirabdollahian reiterated that Iran would "soon" return to the stalled nuclear talks in Vienna, declining to give a date.