Catholic Charities USA, the Catholic Legal Immigration Network and the U.S. Conference of Catholic Bishops sent John Kelly a private letter over a year ago, warning him of the dangers of separating children from families, according to a Buzzfeed News report out this week.

Mr. Kelly, now President Trump’s chief of staff, was secretary of Homeland Security at the time he received the letter. Mr. Kelly said D.H.S. was considering a family separation approach to deter unauthorized immigration during a CNN interview on March 7.

“As you know, family unity is a cornerstone of our American immigration system and a foundational element of Catholic teaching,” the Catholic organizations wrote in a letter dated March 17, 2017, which Buzzfeed obtained through a Freedom of Information Act lawsuit filed against D.H.S. That same month, more than 180 national and local organizations signed a public statement asking Mr. Kelly to reconsider plans to separate families.

The letter may have had changed Mr. Kelly’s mind for a time.

“We believe that separating families would be extremely detrimental to basic child welfare principles, contrary to our Catholic values and ineffective to the goals of deterrence and safety,” the two-page letter read. “We urge you to reject his harmful policy.”

Donna Markham, O.P., president of Catholic Charities USA, Bishop Joe Vásquez of Austin, Tex., chairman of the U.S. bishops’ migration committee, and Bishop Kevin Vann of Orange, Calif., chairman of CLINIC, signed the private letter.

The letter may have changed Mr. Kelly’s mind for a time. A little over a week after the letter from Catholic leaders, Mr. Kelly told Senate Democrats the administration would not separate children from parents at the border.

Trump administration officials said that 2,342 children had been separated from 2,206 parents.

Trump administration officials said that 2,342 children had been separated from 2,206 parents at the U.S.-Mexico border between May 5 and June 9 as part of the policy, according to Catholic News Service. Mr. Trump signed an executive order on June 20 rescinding the policy. While families would no longer be separated, according to the executive order, they may be detained together during the process of prosecution and deportation at the border.

The administration was given until July 10 to reunite children under the age of 5 with their families, but administration officials said on July 9 that they would not be able to meet that deadline. The administration has until July 26 to reunite all of the more than 2,000 children who have been separated from parents.

“The children who are separated from their parents need to be reunited. That’s already begun and it’s certainly not finished and there may be complications, but it must be done and it’s urgent,” said Cardinal Daniel N. DiNardo of Galveston-Houston, president of the U.S.C.C.B., on July 2 after visiting detained migrant children.

Material from Catholic News Service was used in this report.

J.D. Long García is a senior editor at America and co-author of Clericalism: The Institutional Dimension of the Catholic Sexual Abuse Crisis.