For tens of thousands of immigrants across the United States with pending immigration cases or legal procedures, the federal government shutdown will put some urgent matters on hold and allow others of less importance to move ahead.

Petitions for political asylum and non-emergency deportation cases are among the matters that could be delayed for months if the shutdown lasts more than a few days, according to immigration lawyers and advocates.

Meanwhile, some services for U.S. citizens and legal residents, which are financed by customer fees, will continue to be provided. Court hearings or other procedures for any immigrant who is in federal custody will also continue on schedule, and the Board of Immigration Appeals will hear requests for emergency relief from deportation as well as appeals for detained immigrants, according to the Justice Department.

Nationwide, 16 immigration courts are closed and 42 remain open, 23 of which handle only cases of detained immigrants.

The asylum process, advocates in the Washington area and elsewhere said, is especially backed up, with about 350,000 cases pending before immigration judges. Even under normal circumstances, most cases take more than a year to complete.

“This is a nightmare. It is already a nightmare, because of the huge backlog in the court system,” said Judy London, a lawyer with the Public Counsel agency in Los Angeles. “When we go into court, we are often told the first available trial date is a year later. This could mean more delays of months, or even another year.”

One of London’s clients is Didier Vakumbua, 43, a medical doctor who fled his native Congo five years ago after he said police jailed and brutalized him for revealing human rights atrocities to foreign monitors. He spent several years in California while his asylum petition worked its way through the system. His wife and children, meanwhile, sought refuge in another African country.

Last week, Vakumbua won his case on appeal and began preparing to fly his family to the United States. Because one child has a brain tumor, he had been granted emergency permission to bring them quickly. But he still needed one more judge’s signature on some paperwork — and after the shutdown Tuesday, that court was suspended.

“I am happy because I finally won my case, but I am frustrated, too,” Vakumbua said Tuesday afternoon, speaking a mixture of French and Spanish. “I have been waiting a very long time to see my family.”

In the Washington area, officials at the American Immigration Lawyers Association expressed similar concerns. They noted that only about 10 percent of asylum applicants are detained and therefore will be allowed to keep any scheduled court date. For the rest, they said, every delay in the judicial process can make a crucial difference.

“Situations change. Memories fade. Evidence gets lost,” said Greg Chen, advocacy director for the association. “If you have a court date now, and it is kicked off the calendar, it could be a matter of life and death.” Chen noted that because of heavy court backlogs, canceled hearings cannot be quickly rescheduled.

Abel Nuñez, executive director of the Central American Resource Center in Northwest Washington, said many of his agency’s clients are involved in more routine matters, such as waiting to become a U.S. citizen or renewing temporary protective status as a refu­gee from conflict. Still, he said, delays in these procedures can also be stressful and confusing.

On Tuesday morning, Nuñez was told that a Salvadoran student in the District, who qualified for legal residency under President Obama’s “Dream Act” order, was scheduled to have her fingerprints and other biometrics taken Wednesday. At first, he was told the service had been canceled by the shutdown. A few hours later, he learned that the tests were being offered after all, and that her appointment was still on.

“It’s good to have a little positive news, but what really worries me is that this fight over the shutdown and other issues is pushing immigration reform out of the picture,” Nuñez said. “There is a lot of friction and smoke in the air, and there are bigger noises out there now. This is taking the focus off immigration, and the window is shrinking fast.”