“The US govt needs to explain how Marzieh Hashemi—a journalist and grandmother—is such a flight risk that she must be incarcerated until she finishes her testimony to a grand jury,” Zarif said in a message posted on his Twitter account late on Monday.
Pointing to the murder of American civil rights leader Martin Luther King Jr. in 1968, he added, "50 years after MLK assassination, US still violates the civil rights of black men and women”.
Family members say Hashemi, 59, was detained at St. Louis' Lambert International Airport on January 13 and then taken by the FBI to Washington.
On Saturday, a US federal judge said that the news presenter was testifying behind closed doors to a grand jury in Washington.
According to reports, the third court session for the jailed US-born journalist will be held on January 23 in Washington.
"On Wednesday, a 23-member jury will be making a decision about my mother," Hashemi's son, Hossein, told Iranian media on Monday.
He said the jury had failed to level any charges against his mother on the two previous occasions, and that she would be freed if the decision continues to evade the body for a third straight time.