U.S. President Donald Trump on Friday defended his decision to halt a legal fight to add a citizenship question to the 2020 U.S. census forms, one day after issuing an executive order directing the Department of Commerce to obtain citizenship data through other means.

Speaking before departing the White House, Trump said he did not "back down" on the citizenship question.

"I backed up because anybody else would have given this up a long time ago," he said.

The once-a-decade census, which aims to tally all people living in the United States, is required by the Constitution in order to draw the boundaries of the legislative districts that elect members to Congress. It also guides the federal government in allocating more than $800 billion in funding for services such as schools and law enforcement.

Experts from the Census Bureau estimated 6.5 million people would not respond if the citizenship question were asked, leading to an undercount of the census.

What is the U.S. Census?

Now, instead of using census workers to tally citizens and non-citizens, the president has ordered federal agencies to provide data for establishing citizenship numbers.

Many opponents of the citizenship question have vowed to fight on. The American Civil Liberties Union (ACLU) has threatened legal action, saying in a statement the organization will "scrutinize [new plans] closely and assess their legality."

Kristen Clarke, president and executive director of the Lawyers' Committee for Civil Rights Under Law, told reporters Thursday that the group would use "every tool in our arsenal to police the administration, should their executive action violate constitutional or legally protected rights."

NAACP CEO Derrick Johnson said the organization was committed to ensuring the census does not systematically undercount communities.

"We are prepared to fight against any plan that effectively turns the census into another form of voter suppression and economic disempowerment in our communities," Johnson said.

In June, the U.S. Supreme Court blocked the citizenship question from the census.

A court majority rejected the government's original justification, but the ruling left open the possibility the Trump administration could try again in the future.

Since 1950, the citizenship question has not been asked of U.S. households.