LOS ANGELES — They sold their homes and possessions, quit their jobs, and left their country — they thought for good. The Iranians, mainly members of their nation's Christian minorities, were bound for a new life in America after what should have been a brief sojourn in Austria for visa processing.

But more than a year later, some 100 of them remain stranded in Vienna, their savings drained, their lives in limbo and the promise of America dead.

Even as the Trump administration continued to pledge help to religious minorities in the Middle East, many of whom face persecution, the United States denied their applications for refugee status in recent weeks.

''It's unexplainable,'' said H. Avakian, 35, an ethnic Armenian Christian who arrived in Austria from Iran 15 months ago and asked that his first name be withheld out of fear for his safety. ''Suddenly they said, 'Now you can't come.' We don't know why.''

Mr. Avakian, who hoped to join his brother, Andre, in Los Angeles, said in a phone interview that he and other refugees were running out of money and descending into depression. ''Most of us cannot go back to Iran; we're in complete despair,'' he said.

Returning to Iran after an attempt to move to the United States would endanger their lives, he and other applicants said, because the government would regard them as enemies of the state.

''We are afraid they will give us a sentence,'' Mr. Avakian said. ''They could put us in jail.''

The Iranians applied to resettle in the United States under guidelines set by a 1989 law known as the Lautenberg Amendment, which offers safe haven to persecuted religious minorities. In the group are ethnic Armenian and Assyrian Christians, Mandeans, and Zoroastrians, most of whom have relatives in the United States who sponsored them.

''We have been inundated with calls from concerned family,'' said Martin Zogg, executive director of the International Rescue Committee's office in Los Angeles, home to the largest Armenian community in the country.

The denials have drawn rebukes from religious leaders, human rights groups and lawmakers from both parties, who charge the United States with failing to live up to its promises and who say the applicants risk arrest and torture if they return home.

Refugee arrivals have slowed to a trickle since President Trump, who took office vowing to overhaul immigration, cut the number of people that the United States agreed to admit. But Mr. Trump also promised to protect religious minorities, particularly Christians, and his administration has condemned Iran's treatment of them.

Enacted in 1989 to enable Jews and Christian minorities from the former Soviet Union to settle in the United States as refugees, the Lautenberg Amendment was expanded in 2003 to include Iranian religious minorities. Austria agreed to serve as a transit point. The applicants cannot work, attend school or receive government benefits while they wait for the United States to process their cases.

Among those denied visas in recent weeks are several elderly and disabled people. As the wait dragged on, many have had to rely on the Roman Catholic Church for lodging and medical treatment, and at least one couple is living in the guest room of the archbishop of Vienna, Cardinal Christoph Schönborn.

''Some of the Iranians have already spent all the money they came with,'' said Michael Prüller, the spokesman for the Archdiocese of Vienna. ''Others see their means dwindle by the day.''

Iran's Constitution proclaims Shiite Islam the official state religion. While it formally recognizes Christians, Jews and Zoroastrians as protected minorities, the government engages in ''systematic, ongoing and egregious violations of religious freedom, including prolonged detention, torture and executions based primarily or entirely upon the religion of the accused,'' according to the 2017 report of the United States Commission on International Religious Freedom, which makes policy recommendations to the president and to Congress.

From 2010 to 2016, according to the report, Iranian authorities detained hundreds of Christians, raiding church services, threatening church members, and imprisoning worshipers and church leaders.

Suhaib Nashi, president of the Mandaean Society of America, said he feared for several Mandean families in the Vienna group. Like the Baha'i, Mandeans, who follow the teachings of John the Baptist, lack even the nominal protections of the Iranian Constitution and are thus particularly vulnerable to persecution and pressure to convert to Islam.

Among the Mandeans marooned in Vienna are three relatives of Peiman Khamisi of Batavia, Ill., who arrived through the Lautenberg Amendment nine years ago. In Iran, his relatives pretended to be Muslim to avoid harassment, performed religious rites in secret and were denied access to higher education, he said.

In late January, Representatives Randy Hultgren, Republican of Illinois, and James McGovern, Democrat of Massachusetts, chairmen of the House human rights commission, urged Vice President Mike Pence to expedite approvals for the Iranians.

After the denials, they called on the Department of Homeland Security to provide an explanation. ''These Iranians are members of religious minorities fleeing a regime that has brutally oppressed their communities since 1979,'' they said in a statement. ''This being the case, they should be presumed eligible for admittance to the United States as refugees under the Lautenberg Amendment.''

According to the amendment, the government must justify a denial ''to the maximum extent feasible.''

But no reason was given, at least not to those stranded in Austria, or to their relatives in the United States. One family was conditionally approved for refugee status in a March 2017 eligibility letter reviewed by The New York Times. Last month, they were given an ineligibility notice that said their application ''has been denied as a matter of discretion.''

A spokesman for United States Citizenship and Immigration Services, the Homeland Security agency that adjudicates the cases, declined to explain why the family was denied, saying only that ''these individuals were subject to the same rigorous process for resettlement as all refugees.''

Applicants are vetted before they apply for an Austrian transit visa. Once in Vienna, they continue the screening process, pass interviews with Homeland Security and undergo medical exams. Typically, it takes a few months to complete the process, and the approval rate is close to 100 percent.

A State Department spokeswoman said in an email that changes to the United States refugee admissions program in 2016 resulted in ''a greater number of denials in the Vienna refugee program.'' She did not elaborate, but other government officials said that the changes entailed enhanced vetting.

The rejections, she said, were unrelated to Mr. Trump's executive orders barring people from several majority-Muslim countries, including Iran, from entering the country. She added that the United States, Austria and others were working together to find alternatives for the group.

Since 2003, about 30,000 Iranians have settled in the United States thanks to the Lautenberg program. In the fiscal year that ended in September, 1,275 Iranians were admitted, compared with 2,323 the previous year. Another 4,500 still in Iran have registered for the program.

Refugee resettlement officials said that evangelical Christians, who make up more than 90 percent of the Lautenberg pool and hail mainly from Ukraine, continue to arrive as usual.

Some of the Iranians have begun to file appeals with the help of the International Refugee Assistance Project, a nonprofit in New York.

Goharek Garmemasihi, an ethnic Armenian Christian in Los Angeles, said that she had sponsored her brother, sister-in-law, niece and nephew. Within months of arriving in Vienna last year, the parents and their teenage daughter were approved. American authorities informed them that their son, then 22, was still under review. ''They decided to wait together,'' Ms. Garmemasihi said.

Fourteen months passed without any word.

In September, officials persuaded the parents and daughter to leave for the United States, assuring them that their son, a 23-year-old university student, would follow soon, according to Ms. Garmemasihi and her nephew, who spoke from Vienna on the condition that he remain unnamed out of fear for his safety.

About 10 days ago, he was notified of the denial. ''It was the worst day of my life,'' he said through tears.

He said an appeal, which he just filed, was his last hope.

''I wish this nightmare ends, that I can open my eyes and see my family,'' he said. ''I just want to be with them again. I don't care what it takes.''