Donald Trump signed a new law intended to punish state hostage takers and help to bring home US citizens held abroad.
The Robert Levinson Recovery and Hostage Taking Accountability Act was named after the former FBI agent who was snatched on Iran’s Kish Island more than 13 years ago while on a corruption investigation.
His family learnt this year that he had died in custody. It has continued campaigning efforts on behalf of other hostages and to seek the return of Levinson's remains.
The US imposed sanctions this month on two senior Iranian military officers who Washington held responsible for Levinson's abduction and death.
The Act was signed by the president on Sunday, a little more than three weeks before the inauguration of his successor, Joe Biden.
The move was welcomed by former hostages and families of detainees for giving the US government extra measures, including enhanced powers to impose sanctions.
"More than 13 years after Bob Levinson was taken hostage by Iranian authorities, imprisoned and treated in [breach] of every human right, and died in Iranian custody, our family is still disgusted that human beings can commit such barbaric acts," Levinson's family said.
“It is our hope that what happened to Bob Levinson, and to our family, will never happen to anyone else because of the Bob Levinson Act, which gives the US government new and stronger tools to punish hostage takers, conduct rescue operations, and give hostage families the support they desperately need.”
Former detainee Nizar Zakka, a Lebanese IT expert who was freed after being detained in Iran for four years over disputed spying claims, described the bill on Twitter as a “big victory”.
The US-based Foley Foundation estimates at least 42 Americans are being held hostage abroad in 11 countries.
They include Siamak Namazi, an oil executive, who has spent five years in an Iranian jail for what his family and supporters say are trumped-up charges of collaborating with a hostile power, the US. He is now the longest-serving US-Iranian prisoner in the country.
His father Baquer was also held after flying to Iran to visit his son, and is barred from leaving Iran after being released on medical grounds.
The foundation, named after journalist James Foley who was kidnapped and killed by ISIS militants in Syria, is urging president-elect Biden to act swiftly on his inauguration next month and keep the issue high on his policy agenda.
Sarah (Levinson) Moriarty, Levinson's daughter, and Diane Foley, Foley's mother, jointly urged Mr Biden to launch a joint review of all active cases and make swift appointments to key positions to ensure that no momentum is lost.
"We ask that president-elect Biden hold accountable any entity that captures and tortures our citizens as a critical deterrent to future hostage taking," they wrote on US political website The Hill.
Mr Trump made the issue a priority of his administration and trumpeted his success in securing the release of prisoners, including Michael White, a former serviceman, from Iran.