U.S. government action could send 100 mostly Christian Iranians stranded in Vienna back to Iran this week, where their return during the harsh government crackdown on dissidents could target them for further persecution, human rights activists warn. The deportation threat looms despite the Trump administration's and Congress's vocal support for protesters in Iran, who are waging the strongest nationwide uprising against the government in Tehran in eight years. "These deportations, during a human-rights crackdown in Iran no less, could be a death sentence for these persecuted Christians and other minorities," Nina Shea, an international humans rights lawyer who directs the Hudson Institute's Center for Religious Freedom, told the Washington Free Beacon. "They would undermine the important statements against Iran's repression by President Trump, Vice President Pence and U.N. Ambassador [Nikki Haley]." "The administration needs to act fast to stop this travesty," she said, noting that the U.S. government could give the refugees notices denying them entry to the U.S. as early as this week. This would leave the Austrians with little choice but to send them back to Iran. Activists say the timing of the deportation threat is also particularly troublesome for the Trump administration, after the State Department last week designated Iran among 10 countries "of particular concern" for "systematic, ongoing, and egregious violations of religious freedom." The Iranian Christian refugees traveled to Vienna in January 2017 under a 27-year-old U.S. law passed by Congress to help Jews escape persecution in the Soviet Union. Under a 2004 update of the law, known as the Lautenberg amendment, the State Department has helped tens of thousands of Iranian Jews, Christians, and Baha'is who were at risk in their home country to resettle in the United States. During the end of the Obama administration, the State Department initially signed off on plans to resettle the latest group of mostly Iranian Christian refugees but then placed a hold on them toward the end of last year before Trump took office, according to Anna Buwalda, executive director of the Jubilee Campaign. The Jubilee Campaign is a nonprofit organization that advocates for religious minorities who suffer persecution in their home countries. Buwalda says she and other human-rights activists don't know why the U.S. appears to be on the brink of denying them entry to the United States, and no one at the State Department or DHS has provided any answers. "This is part of the mystery, and nobody's been able to receive any information to explain it," she said. One-third of the refugees were set to resettle in California, where many of their relatives who have already gone through the refugee resettlement process are located, according to the activists. The Department of Homeland Security, which has an office in Vienna, helped interview and vet the refugees, along with HIAS, the global Jewish nonprofit that works with the State Department on Lautenberg program refugee cases, Buwalda said. HIAS referred a request for comment to its partner, the State Department Bureau of Population, Refugees and Migration. Neither the State Department nor the DHS provided a response. The refugees, most of them Armenians and Assyrians, have been waiting in Vienna for a year as U.S. courts have weighed in on the constitutionality of the travel ban, and recently were informed they must go back to Iran, according to Shea and Buwalda. It is unclear if the Trump administration is behind the deportation threat or if Austria is becoming impatient with these cases remaining in limbo. Human rights groups are urging the administration to take action and are worried the refugees and other priorities involving religious minorities in hotspots around the world are falling through the cracks as key Trump administration posts remain vacant a year into his presidency. "The U.S. has broken its promise to Iranian religious minorities," Buwalda said. "They traveled to Vienna at the invitation of the United States, with the understanding that they would soon be reunited with their American families. Instead, the groups of refugees have been forced to wait there for more than a year with no explanation. They have no source of income, and many have spent down their life savings." "The U.S. government must solve this situation quickly and humanely," she said. One key post that would normally handle Lautenberg program issues remains vacant. Kansas Gov. Sam Brownback's nomination to the State Department post of ambassador at large for religious freedom is in limbo after Democrats placed a hold on it late last year and blocked the Senate from approving him. The White House re-nominated Brownback on Monday but has not publicly disclosed whether it intends to expend the political capital to lean on the Senate to quickly confirm him. Senate GOP leaders would have to devote at least three days of precious floor time to hold a floor vote on the nomination if Democrats continue to oppose him instead of passing him quickly by unanimous consent. The White House did not respond to an inquiry into Brownback's nomination. Catholic and other Christian leaders have praised the Trump administration's rhetoric on the issue. They point to the administration's National Security Strategy report, unveiled in late December, and its pledge to "protect religious minorities" abroad. Pence in October received a standing ovation at a dinner devoted to religious freedom issue when he pledged that "help is on the way" to religious minority communities in Iraq struggling to recover from Islamic State genocide. However, Trump also has yet to appoint a special adviser for international religious freedom at the White House's National Security Council and has kept a special envoy for religious freedom post downgraded in power, as it was during the Obama administration. The faith office at USAID also remains without a leader. Update 12:07 p.m.: This post has been updated to remove a line implying the group of 100 individuals were being held up by various court rulings on the Trump travel ban. The holds on this group happened at the end of the Obama administration and are unrelated to the travel ban.