SEATTLE — A federal judge said he would decide before Christmas whether to stop a Trump administration ban on certain refugees after hearing arguments Thursday that the ban is separating families and putting some refugees in danger.

Lawyers from the ACLU and Jewish Family Service asked US District Judge James Robart for an injunction on a ban the administration has placed on refugees from some mostly Muslim countries.

The ban went into effect in October after President Trump issued an executive order resuming the refugee program ‘‘with enhanced vetting capabilities.’’

The day before that order, Secretary of State Rex Tillerson, then-Acting Homeland Security Secretary Elaine Duke, and Director of National Intelligence Daniel Coats sent a memo to Trump saying certain refugees must be banned unless additional security measures are implemented.

The banned refugees include the spouses and minor children of refugees who have already settled in the United States. The action also suspended the refugee program for people coming from 11 countries, nine of which are mostly Muslim.

The ACLU argued the memo provided no evidence for why additional security was needed and didn’t specify a timeframe for implementing the changes.

‘‘Refugee resettlement is one of our proudest humanitarian achievements,’’ Mariko Hirose, a lawyer with the ACLU, said after the hearing.

‘‘We as Americans cannot let this administration destroy our refugee program and repeat the worst of this country’s history by letting bigotry turn away those who need our help the most,’’ she said.

August Flentje, with the Department of Justice, told Robart that the ban is temporary and ‘‘is a reasonable and appropriate way for agency heads to tackle gaps’’ in the screening process.

But Robart questioned whether Trump administration policies were trampling the Administrative Procedure Act, which says a process must be followed before shutting down a program.

The judge also questioned whether the Department of Homeland Security has the authority to stop the refugee program, when the Immigration and Nationality Act, passed by Congress, mandates the reunification of the families of refugees settled in this country.

After peppering the lawyers with questions, Robart said he is taking the motion for a preliminary injunction under advisement and would issue a ruling by Christmas, which is only one business day away.