The US government has announced a new plan to detain illegal immigrant children indefinitely with their parents.
It proposed a termination of the so-called Flores Agreement, a court ruling that requires it to release minors after a maximum 20 days in detention.
The move was the latest twist in a saga which saw 2,900 children separated from their families at the Mexican border earlier this year under Donald Trump’s "zero tolerance" immigration policy.
Immigration advocates oppose any effort to detain children longer than the current agreement allows, and will almost certainly challenge the latest development in court.
The Flores Agreement came about in 1997 and resulted from a legal case involving a girl from El Salvador who was detained.
The 20-day limit led to a situation in which illegal immigrants crossing the border with children were generally released from custody after a short period of time.
Under Mr Trump’s "zero tolerance" policy children were separated from their parents, so that the parents could be detained for longer.
That led to an international outcry and Mr Trump ultimately reversed the policy.
However, hundreds of children remain separated from parents who were deported without them, and efforts to reunite them continue.
If the new policy were to proceed, the government only currently has three operational family detention centres.
The homeland security department has asked for space to house 12,000 families, plus space for 20,000 unaccompanied minors.
Families would then be held together until their immigration cases were completed.
Under the proposal children would be "treated with dignity, respect and special concern," the department said.
Kirstjen Nielsen, Mr Trump’s homeland security secretary, said: "Today, legal loopholes significantly hinder the department’s ability to appropriately detain and promptly remove family units that have no legal basis to remain in the country.
"This new rule addresses one of the primary pull factors for illegal immigration, and allows the federal government to enforce immigration laws as passed by Congress."