Foreign Ministry spokesman Ramin Mehmanparast on Tuesday insisted there "is no relation" between the two. He says the American sanctions "have yet to be put into practice."
The Iranian currency's exchange rate hovered late Monday around 18,000 riyals to the dollar, marking a roughly 12% slide compared to Sunday's rate of 15,900 riyals to the dollar.
US President Barack Obama on Saturday signed into law a bill targeting Iran's central bank as part of the West's efforts to pressure Tehran over its nuclear program. It goes into effect in six months.
Eighty percent of the income of Iran, OPEC's second oil exporter after Saudi Arabia, depends on its oil sales to foreign countries.
The European Union is considering banning the purchase of oil from Iran. A decision on the matter may be made at the EU's foreign ministers conference at the end of the month.