In a stunning move, the Obama Administration has thrust itself into the middle of the explosive federal stop-and-frisk trial and is taking sides against the NYPD, raising the odds of a outside monitor being appointed to oversee the controversial crime-fighting program.

“This is very bad news,” said one City Hall source.

The source said that Attorney General Eric Holder’s office notified the city that it intends to file briefs in support of claims by the Center for Constitutional Rights that cops are stopping suspects on the basis of race.

Ten weeks of testimony in the case concluded last month.

But the federal government has the right to intervene in any federal case and Holder’s office will do so before the end of the day, the last day for filing briefs, the source said.

The presiding judge, Shira Schiendlin, has yet to issue a ruling.

City officials feel privately that the NYPD held its own during the trial, leading to the hope that the judge would stop short of naming a monitor.

“This gives her the cover to do that,” said one concerned source.