Washington (CNN) The Trump administration is considering a plan to limit most, if not all, members of the group of migrants in Mexico heading toward the United States from crossing the border.

A Department of Homeland Security official tells CNN the administration could limit the number of migrants able to enter at legal ports of entry. DHS would do this by "metering," essentially creating a waitlist to allow people to enter only if the department has the capacity to process and detain them at one of its facilities.

Those who are allowed to enter the US -- if they enter as a family -- may be given a stark choice.

The administration is considering immediately giving those asylum seekers the option either to be detained together as a family during immigration proceedings or be separated from their kids, who would go into the care of the Department of Health and Human Services.

In the past, the practice of metering has resulted in individuals deciding not to endure a lengthy wait to try to get into the country legally and instead to cross illegally. Should some of this group of migrants do the latter, they could face a tougher and higher standard for seeking asylum under the administration's plans.

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