(CNN) Administration officials are weighing a proposal that could result in parents and kids once again being split up by the US government -- but this time, it would be the parents' choice.

The proposal would give detained immigrant families two options: remain detained together while their case works its way through the system, or allow children to be released from custody after 20 days while their parents stay behind bars.

The administration is weighing whether to start a pilot program to see how it would work and how parents would proceed with their decisions, a senior Department of Homeland Security official told CNN Monday.

Known as "binary choice," the proposal drew widespread attention -- and sharp condemnation from advocacy groups -- when it was reported by The Washington Post on Friday. But it isn't a new idea. It came up in court filings back in July.

There are still more questions than answers about this latest policy push. Here's what we know so far:

A pilot program is under consideration, but it hasn't started yet

Specific details like location and length of a pilot program are still being discussed internally, the senior DHS official said. It has not started yet. If implemented, a "binary choice" policy would be new.

The reasoning for this proposal, officials have said, is twofold:

1) Immigrant children can only be detained for 20 days under a 1997 court settlement, but officials don't want that to limit how long they can hold families.

2) Officials are trying to deter increasing numbers of families crossing the border.

But "binary choice" isn't the only thing officials are doing to deter undocumented migrants from traveling to the US.

Officials have also been placing advertising in Central America to warn would-be migrants of the dangers of the journey. Mexico has also been cooperating "to a degree," the senior DHS official said, by stopping people trying to enter Mexico from Guatemala.

White House adviser Stephen Miller has been pushing internally for the "binary choice" option to be implemented, but officials haven't decided yet if they're going that route, a senior administration official told CNN's Liz Landers on Friday.

Trump wouldn't give a straight answer when asked whether his administration plans to separate families again.

Is the administration on the verge of renewing its efforts to separate families? The issue came up in Trump's "60 Minutes" interview Sunday, and his comments were anything but clear.

"When you allow the parents to stay together, OK, when you allow that, then what happens is people are gonna pour into our country," Trump said.

"So are you gonna go back to that?" Stahl asked.

The administration is "looking at a lot of things," Trump replied.

Stahl pressed the President to give a "yes or no" answer on whether the administration plans to return to separating migrant families.

"I will only -- I can't -- you can't say yes or no," Trump said. "What I can say is this: There are consequences from coming into a country, namely our country, illegally."

Officials have been talking about doing this for months. And a judge signed off in August.

We got our first hint this could be in the offing back in July, when government attorneys filed paperwork indicating as much in federal court in California.

A 1997 federal court settlement bars ICE from keeping minors in custody for more than 20 days. The Trump administration has been trying to get around this on multiple fronts, including efforts to write a new federal regulation to nullify it.

But in the meantime, government attorneys asked for an assist from US District Judge Dana Sabraw, who's been weighing an ACLU class action lawsuit over family separations. Sabraw ordered the government to reunite most of the families it separated in June and has been holding regular hearings to monitor officials' progress.

In a joint motion, ACLU and government attorneys asked Sabraw to agree that his ruling requiring officials to reunite separated families didn't limit the government's discretion to detain parents. That motion outlined the plan that's now described as "binary choice."

Sabraw signed off on that motion with a court order in August

As details emerged about the proposal in recent days, advocates swiftly slammed it.

"Forcing families to choose between indefinite incarceration and family separation is no choice at all," Human Rights First said on Twitter . "Instead of employing effective and human strategies, the administration wants to rain cruelty on fleeing families."

Detaining more families is harder than it sounds.

Separating families is the part of this proposal that's getting the most attention. But there's also a flip side.

"Binary choice," as its been outlined, could also lead to an increasing number of families being detained.

And there's a major logistical hurdle the administration faces if it moves forward with a plan to detain more families: finding space.

ICE has three family detention centers -- two in Texas and one in Pennsylvania. Together they can hold about 3,000 parents and kids. But more than four times that many family members were apprehended in August alone, according to CBP

Administration officials have already warned they're out of space and have been releasing families they don't have room to detain. But the senior DHS official said there's enough family detention space to start a pilot program.

The issue, according to the official, is that Health and Human Services facilities for unaccompanied and "separated children," are at capacity.