Foreign countries have arrested and detained a growing number of American nationals that currently remain hostage abroad.

The number of foreign governments currently holding Americans hostage largely surpasses citizens being detained by terrorist and militant groups, according to the James W. Foley Legacy Foundation. There are at least 43 U.S. nationals held hostage by governments abroad while there are only nineteen known cases of Americans currently being detained by militant and other criminal groups.

Experts say China, North Korea, Iran, Cuba and Venezuela are the most prominent nations taking foreign nationals hostage, according to the Washington Post.

American journalist Salah al-Haidar and his mother Aziza al-Yousef are currently detained in Saudi Arabia for their connections to women’s rights activism, according to the outlet. The two were released from prison but are barred from leaving the country as the nation faces criticism from President Joe Biden’s administration regarding their human rights records, Reuters reported.

Former U.S. Marines Paul Whelan and Trevor Reed are being held in Russian forced labor camps, according to CNN. Whelan was arrested by Russian authorities in 2018 for allegedly being involved in an intelligence operation and Reed was detained in 2019 for allegedly endangering Russian law enforcement during a drunk altercation. (RELATED: American Political Prisoner Asks Russian Court To Serve Sentence In US: REPORT)

Venezuela offered to release six imprisoned Americans in 2020 in exchange for the U.S. to free Alex Saab, a key financier of President Nicolas Maduro, the Associated Press reported. Richard Grenell, a close ally of former President Donald Trump’s administration, denied the offer.

The rejection resulted in the Venezuelan government re-imprisoning six American oil executives of their state owned oil company, CITGO, according to the outlet. The prisoners had formerly been under house arrest since 2017. In addition to the CITGO executives, three other detainees—Luke Denman, Airan Berry and Matthew Heath—remain hostages in by the Venezuelan government.

Foreign governments taking Americans hostage is a problem that keeps getting worse. A @PostOpinions⁩ team led by ⁦@kwoodsome⁩ set out to find out why and what needs to happen to stop it. And why it matters. #BringThemHome https://t.co/Pkic59sA6R

— Jason Rezaian (@jrezaian) November 8, 2021

At least four Americans with dual citizenship in Iran are imprisoned by the Iranian government, including American-Iranian businessman Emad Sharghi after the Tehran court convicted of espionage and sentenced to ten years in prison without a trial, NBC News reported.

The Chinese government threatened to detain U.S. nationals in response to the Justice Department prosecuting Chinese scientists for concealing their active duty statuses from U.S. immigration officials in 2020, according to the Wall Street Journal. China has denied U.S. citizens permission to leave the country in the past and have arrested nationals for “bogus allegations.”

Former Obama-era deputy national security advisor Ben Rhodes said the hostage issue threatens the U.S.’ diplomacy with other nations, according to the Post.

“The reason to take this seriously is in part because, yes, there are individual lives at stake here, but it’s also something that is reaching such a scale that it’s going to begin to pollute international commerce, international diplomacy,” Rhodes said. “I mean, this system in general is creaky, and then when you have a superpower-which is what China is-beginning to engage in it, too, I don’t know how many more warning signals you need.”

Congress codified the Robert Levinson Hostage Recovery and Hostage-Taking Accountability Act in December 2020, which intends to track and recover all hostage cases involving U.S. citizens and impose sanctions on any foreigner responsible for wrongfully detaining a U.S. national.

The legislation is named after the part-time CIA consultant who was held hostage by the Iranian since 2007 after traveling to the island of Kish to meet with an official. Former national security advisor Robert O’Brien informed Levinson’s family that they believed he had died “some time ago” in Iranian captivity in March, 2020.

Roger Carstens, the current hostage envoy appointed during the Trump administration, said foreign nations like Iran detain Americans for “leverage,” the outlet reported. The number of reported hostage cases has steadily increased in part to the government’s ability to track these cases and become more aware of wrongful arrests abroad.

Former President Barack Obama ordered a review of the U.S. hostage recovery to process four Americans in 2014, including journalist James Foley, who were beheaded by members of ISIS, according to the Post. The administration formed the interagency Hostage Recovery Fusion Cell, the Office of the Special Presidential Envoy for Hostage Affairs and the National Security Council’s Hostage Response Group.

In an October 25 letter, families of the over two dozen hostages questioned President Joe Biden’s efforts to return their loved ones home, The Associated Press reported. The families stated they have been unable to reach the president or his national security advisor, Jake Sullivan.

“We need to be shown that the promises of your administration to prioritize the return of our family members are not empty,” the letter said. “Now is the time for action. Now we need you to bring our fellow Americans home.”