For once in their contentious "sanctuary city" court battle, the city and federal governments agree on something:

They don't like the compromise suggested by the judge.

The Trump administration doubts that "further attempts at negotiations with the city would be productive" and thinks the best answer is for the city to change its policies, wrote senior trial counsel Daniel Schwei of the U.S. Justice Department.

The city is "not willing to modify its policy" in regard to a key issue, and the federal government is trying to impose unlawful conditions, wrote Virginia Gibson, representing Philadelphia.

This month, U.S. District Judge Michael Baylson tried to push the Trump and Kenney administrations toward compromise, calling the case "a paperwork dispute" that could "be solved with the stroke of a pen."

The Trump administration wants to withhold about $1.5 million in law enforcement grant money unless the city agrees to actively assist federal authorities in identifying and turning over undocumented immigrants. The city sued in the summer of 2017, saying the Police Department is not an arm of immigration enforcement, and making it one would damage community relations.

>> READ MORE: Philly's sanctuary city status on trial

A key issue is the city's refusal to honor Immigration and Customs Enforcement detainers for people who are being released from custody, viewing those papers as administrative requests, not binding. The city says it will respond to a detainer only if that paperwork is accompanied by a signed warrant from a judge.

The Trump administration argues that city policies allow dangerous criminals to be released into the community, when they should be deported to their homeland. It wants the city to hold people on detainer until ICE agents can get there.

On May 10, as testimony concluded, Baylson said he thought the sides could find a third path, one that would demand minimal concessions. He warned that if the sides could not agree on a compromise, he might do it for them.

The judge said an undocumented immigrant who has never been convicted of a crime, and who is being released on bail or his own recognizance, is entitled to due process under the law.  But, he said, an undocumented immigrant who has been convicted of a crime, and is being released from prison or being released on bail after being charged with a new crime, is a different matter.

A "criminal alien" has no rights under the law, Baylson said.

The judge suggested that, in filing a detainer, ICE could provide information establishing the criminal convictions of the person it wants held. And that the city could agree to turn over undocumented immigrants for whom ICE provided a detainer and proof of criminal conviction.

On Monday the judge told the sides to file legal briefs no later than Friday. It's unclear when he might rule.