The chief executive of the nation's largest shelters for migrant children said Tuesday he fears a lack of urgency by the U.S. government could mean it will take months to reunite thousands of immigrant children with their parents.

Juan Sanchez of the nonprofit Southwest Key Programs said the government has no process in place to speed the return of more than 2,000 children separated from their parents as part of the Trump administration's recent "zero-tolerance" crackdown on illegal immigration.

"It could take days," Sanchez said Tuesday in an interview with The Associated Press. "Or it could take a month, two months, six or even nine. I just don't know."

A judge in California ordered U.S. border authorities to reunite separated families within 30 days of the ruling issued late Tuesday. If children are younger than 5, they must be reunified within the next 14 days.

The communications staff at the U.S. Department of Health and Human Services didn't reply to a request for information about how long the process would take. During Congressional testimony on Tuesday, HHS Secretary Alex Azar declined to be pinned down on how long it would take to reunite separated families. "We have to expeditiously get children out of our care," he said.

Sanchez said Southwest Key is "ready today" to do what it takes to reunite children with parents who have been arrested for trying to cross the U.S.-Mexico border. But he said his group is limited in what it can do because many parents' cases will likely have to make their way through the legal system before the federal Office of Refugee Resettlement can give the go-ahead to put families back together.

Newly planned family detention space could allow recently separated children to be housed with their parents, Sanchez said, adding that would not be optimal, but would be better than keeping them apart.

"If it was me," he said. "I'd say I want the child with me."

Sanchez finds himself in the center of political controversy after agreeing to take in more than 600 children who were stripped from their parents as part of the Trump administration's anti-immigration push.

Of those, 152 are younger than 5, including some babies and toddlers. The rest are between 6 and 11 years old.

Currently Southwest Key has nearly 5,100 children in 26 shelters in Texas, Arizona and California, accounting for nearly half the unaccompanied minors being held in facilities all over the country. Most of them are older children who weren't taken from their parents but instead tried to cross the border on their own.

Undocumented immigrant families are released from detention at a bus depot in McAllen, Texas, U.S., on June 25, 2018. REUTERS/Loren Elliott

The nonprofit organization has booked $458 million in federal contracts during the current budget year — half of what is being handed out by HHS for placing immigrant children who came to the U.S. unaccompanied or were separated from their families after arriving.

Southwest Key, meanwhile, is hoping to get a green light for a new "tender age" shelter in a Houston warehouse previously used for Hurricane Harvey evacuees.

The Texas Health and Human Services Commission said it could take three weeks to inspect the site and another two months to decide whether a permit will be issued.

Sanchez said he opposed the family-separation policy, but for the sake of the children he felt his organization needed to take them in.

"Somebody has to take care of them," he said.