WASHINGTON — The Supreme Court agreed Friday to take up an aspect of the legal battle over the Trump administration's plan to put a question about citizenship on the 2020 census form.

Eighteen states, several of the nation's largest cities and immigrant rights groups brought the lawsuit. They said adding the question would making immigrants reluctant to respond to census takers, resulting in an undercount of that segment of the population.

A federal district court judge in New York, Jesse Furman, is now holding a trial to decide if the citizenship question can be included on the form.

The Supreme Court said Friday it would decide whether the judge could include, as part of the evidence, depositions from senior government officials about why they want the question to be part of the census.

That trial is almost over, and the Supreme Court won't hear argument over the evidence issue until Feb. 19. Furman may have to delay his ruling until the Supreme Court resolves the question, or he could decide that the disputed evidence would make no difference to the outcome of the trial.

The government has pressed for a quick resolution to the case, because the printing of the forms must begin early next year.

Conducted every 10 years, the census is required by the Constitution. The results determine the size of each state's delegation in the House of Representatives and are used in calculating a state's share of funds under many federal grant programs.