McALLEN, Texas (AP) — After President Joe Biden this summer announced a new U.S. citizenship pathway for immigrant spouses, Oscar Silva rushed to apply and was elated Monday when an email arrived confirming his appointment for a required biometric exam.

But hours later, Silva received a jolt: a federal judge in Texas was temporarily suspending the program that could benefit an estimated 500,000 immigrants in the U.S., freezing in place one of the biggest presidential actions to ease a path to citizenship in years.

"I don't know what is going to happen," Silva said Tuesday. The 23-year-old college student arrived in the U.S. as a baby and lives in Texas with his wife, Natalie, an American citizen who provides for their family as a high school teacher.

Although the Biden administration's "Keeping Families Together" program only began accepting applications last week, families and immigration attorneys say confusion, uncertainty and frustration is already mounting following the order by U.S. District Judge J. Campbell Barker. Couples who already applied say they are in limbo and those who haven't yet must weigh whether to wait for Republicans' court challenge over the program to play out.

Applicants must pay a $580 processing fee. Following Barker's order, the Florida Immigrant Coalition said it was asking people "to weigh their options and to make the best decision for their families at this time."

The court order followed a challenge by 16 states, led by Republican attorneys general, who filed a federal lawsuit days after the program began taking applications on Aug. 19. Barker's order, known as an administrative stay, will be in place for 14 days but could be extended.

"That ruling is wrong. These families should not be needlessly separated," Biden said in a statement.

The states claimed the move would cause irreparable harm and accused the administration of bypassing Congress for "blatant political purposes."

Republican Texas Attorney General Ken Paxton, whose office is helping lead the lawsuit, applauded the order. "This is just the first step. We are going to keep fighting for Texas, our country, and the rule of law," he said in a statement.

On Tuesday, the Department of Homeland Security said the government would continue to take applications and defend the program in court. Any applicants whose parole was granted prior to the order will be unaffected, according to the department.

DHS did not respond to questions about how many applications were received or approved or how long it takes to determine the outcome of a case under the program.

Fears of separation returned for Silva and his wife, Natalie. Under the traditional process to apply for a green card, spouses living in the U.S. illegally can be required to return to their home country — often for years — and they always face the risk they may not be allowed back in.

"We thought this was finally our opportunity to be able to go through this process together and not fear the possibility of spending ten years away from each other," Silva said. Now "I feel pretty heartbroken, very sad… because without it we face so much uncertainty."

Immigration attorney Laura Flores-Perilla said it was "really unclear" what will happen with Silva's appointment scheduled for September.

"I cannot underestimate the impact that this temporary pause is having," said Flores-Perilla, an attorney at the Action Justice Center.

Gregory Chen, the director of government relations for the American Immigration Lawyers Association, said he had heard from lawyers affiliated with the association of at least hundreds of people who had applied since the program was launched, including some who applied and were approved the next day.

Lawyers are rushing to understand what the order means for their clients, too. According to Chen, the organization's listserv for lawyers interested in the Keeping Families Together program "blew up" after the judge's decision late Monday with questions about what the decision means.

Advocates are concerned the changes, even temporary ones, created by such litigation "creates chaos and uncertainty" for those looking to apply. Chen said he's seen the effect litigation has had on other immigration-related programs.

His organization has held three webinars designed to educate lawyers about the program. One of those seminars had about 1,000 lawyers in attendance, an extremely high number for one of the group's educational offerings, Chen said.

Roberto García, 37, and his wife Maria in Los Angeles had just paid an attorney $3,000 to help them fill out the lengthy application for the program but the application wasn't submitted yet because of Monday's order. Now, they're wondering if they should gamble their chances and pay the processing fee for a program on hold.

"I didn't think this was going to happen. It's very hard," said Roberto Garcia, referring to the order that halted the parole program. "We are not a priority. It is bad that they play with people's feelings."

Roberto is the sole provider for the family of five and earns a living through this construction business in California. He also sends money back home to family in Mexico.

If approved, applicants have three years to seek permanent residency. During that period, they can get a work authorization.

But Maria García said she is losing hope and considering moving to Mexico, where her husband has his parents and brothers.

"We will never be able to buy a house here," she said. "Here if you do things wrong, they reward you. If you do things right, they punish you."

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Salomon reported from Miami. Associated Press writer Rebecca Santana in Washington contributed to this report.