The Iranians have demanded consular access to Manssor Arbabsiar, the man accused of involvement in the plot to kill the Saudi ambassador.
Arbabsiar holds dual American-Iranian citizenship.
President Barack Obama said Thursday that Iran -- already at odds with Western governments over its nuclear program -- would face the toughest possible sanctions and the United States would not take any options off the table, the standard code to refer to possible military action.
Iran's Foreign Ministry summoned the Swiss charge d'affaires who represents U.S. interests in the country that broke ties with Washington shortly after the 1979 Islamic revolution.
"There is no doubt regarding the baselessness of the U.S. allegations," a ministry official told the Swiss representative, according to state broadcaster IRIB.
"However, providing personal information about the accused and consular access to him is among the duties of the U.S. government. Any delay in that respect would be in contravention of international law and the U.S. government's responsibilities," the unidentified official said.
Iran's diplomatic interests in the United States are handled by an office in the Pakistani embassy.
Arbabsiar is entitled under international law to consular access because of his Iranian citizenship.
The chances of military action against Iran are slim and none. The Obama administration isn't even likely to impose tougher sanctions on the Iranian central bank which might be effective because payments for Iranian oil is processed there.
As usual, they are talking big and doing little.