President Joe Biden's national-security adviser, Jake Sullivan, said on February 21 that the new administration has "begun to communicate with the Iranians" on the issue of detained Americans.
Speaking on a weekend current-affairs program, Sullivan said Washington's "strong message to the Iranians will be that...we will not accept a long-term proposition where they continue to hold Americans in an unjust and unlawful manner."
The United States has repeatedly called on Iran to help locate former FBI agent Robert Levinson, who disappeared when he traveled to the Iranian resort of Kish Island in 2007 and is presumed dead.
At least four other American-Iranians are thought to still be in Iranian custody, including businessmen Emad Sharghi and Siamak Namazi.
"It will be a significant priority of this administration to get those Americans safely back home," Sullivan said.
The United States and other Western governments have long accused Tehran of detaining dual nationals who visit Iran and other foreign nationals -- frequently on dubious espionage charges -- in order to use them as bargaining chips for prisoner swaps.
"We intend to very directly communicate with the Iranians about the complete and utter outrage, the humanitarian catastrophe that is the unjust, unlawful detention of American citizens in Iran," Sullivan said on CBS's Face The Nation program. "We have begun to communicate with the Iranians on this issue, yes. And we will continue to do so as we go forward."