The US Justice Department has said it will continue to search for legal grounds to force the inclusion of a citizenship question on the 2020 census.
It comes hours after President Donald Trump said he was “very seriously” considering an executive order to get the question on the form.
The Justice Department did not say exactly what options remain now that the Supreme Court has barred the question at least temporarily.
The government has already begun the process of printing the census questionnaire without that question.
The Trump administration’s focus on asking broadly about citizenship for the first time since 1950 reflects the enormous political stakes and potential costs in the once-a-decade population count that determines the allocation of seats in the House of Representatives for the next 10 years and the distribution of some 675 billion US dollars (£539 billion) in federal spending.
It also reflects Mr Trump’s interest in reshaping how congressional districts are drawn.
Districts are currently based on the total population, but some Republicans want them based on the population of eligible voters, a change that could disadvantage Democrats by excluding immigrants.
The Supreme Court has left open the issue of whether districts based only on the population of eligible voters is constitutional.
The Census Bureau’s own experts have said a citizenship question would discourage immigrants from participating in the survey and result in a less accurate census that would redistribute money and political power away from Democratic-led cities where immigrants tend to cluster to whiter, rural areas where Republicans do well.
Mr Trump, speaking as he departed the White House for a weekend in New Jersey, said he might take executive action.
“It’s one of the ways that we’re thinking about doing it, very seriously,” he said.
An executive order would not, by itself, override court rulings blocking the inclusion of the citizenship question.
But such an action from Mr Trump would perhaps give administration lawyers a new basis to try to convince federal courts that the question could be included.
“Executive orders do not override decisions of the Supreme Court,” Thomas Saenz, president and general counsel of the Mexican American Legal Defence and Educational Fund, said in a statement on Friday. The organisation is representing plaintiffs in the census lawsuit in Maryland.
Later on Friday, Justice Department lawyers formally told US District Judge George Hazel in Maryland that the administration was not giving up the legal fight to add the citizenship question to the next census. But they also said it was unclear how they would proceed, according to a court filing.
“They still say they don’t have clear instructions on what to do,” said Mr Saenz, who took part in a conference call with the judge and lawyers for both sides in one of three lawsuits seeking to keep the question off the census. The other two are in New York and California.
The judge had expressed mounting frustration with the mixed signals the administration was sending, first telling him on Tuesday that the question was off only to have Mr Trump tweet the next day that the administration was “absolutely moving forward” with efforts to include the question.
On Friday evening, the American Civil Liberties Union asked a federal judge in New York to permanently block the administration from adding the citizenship question to the 2020 census.