US President Joe Biden signed an executive order on Tuesday aimed at deterring and punishing wrongful detention of US citizens abroad by authorising government agencies to impose sanctions and other measures.
Mr Biden has faced growing pressure from families of hostages and detainees, most recently on the case of WNBA star Brittney Griner, who has been held in Russia since February and is on trial on drug charges.
Deteriorating ties between the US and Russia over Moscow's invasion of Ukraine highlighted her detention and the wider issue.
The US does not provide an official figure for how many US citizens are detained abroad.
But the James Foley Legacy Foundation, named after an American journalist abducted and killed in Syria, says that more than 60 US citizens are wrongfully detained in about 18 countries.
Some are held by top US adversaries such as Iran, Russia, Venezuela and China.
Mr Biden was "committed to getting all these cases resolved and … at the same time, start to bring up a deterrence strategy that can raise the cost of hostage-taking and wrongful detention", a senior administration official said.
The executive order authorises agencies to impose unspecified costs and consequences, including financial sanctions, on those involved in taking hostages.
"The sanctions authority included in this [order} enables the United States to impose financial and travel sanctions on those who are responsible for unjustly holding US nationals, whether their captor is a terrorist network or a state actor," Secretary of State Antony Blinken said.
The order directs government agencies to work more closely with detainees' families and share information and possibly intelligence, US officials say.
As part of the new steps, State Department travel advisories will add warnings when there is an increased risk of wrongful detention in a foreign country.
Myanmar, China, Iran, North Korea, Russia and Venezuela will receive the warning on Tuesday.
The administration held a video call on Monday with family members of detainees to preview the executive order, some who took part said.
Several were disappointed, saying they were not allowed to speak on the call and were sceptical that the order would be effective.
The order "appears to concern deterring future cases more than solving the current ones", one said.
Russia's release in April of former US Marine Trevor Reed intensified calls by relatives of others held overseas for Mr Biden to act.
Mr Reed was freed after three years of detention as part of a prisoner swap with Russia. Mr Biden commuted the US prison sentence of Russian pilot Konstantin Yaroshenko.
