Yemen Raid That Likely Killed Civilians Was 'Well Thought Out,' White House Says "This was a very, very well thought out and executed effort," Sean Spicer said.

 -- The White House characterized Sunday's deadly raid in Yemen that likely killed civilians as "a very, very well thought out and executed effort."

On Thursday, press secretary Sean Spicer took reporters through a timeline of events leading up to the mission. Spicer said the planning of the mission began back in November under the Obama administration, but it was not carried out until this past weekend because officials were waiting for a moonless night.

The raid, which was authorized by President Donald Trump, has been the subject of some criticism, with some alleging that it was approved without sufficient intelligence. Spicer pushed back against those reports Thursday.

"It was ... a very, very thought out process by this administration. It ... was moved forward by Centcom on Nov. 7. This was a very, very well thought out and executed effort," Spicer said, referring to the U.S. Central Command.

The raid, carried out by members of the elite unit SEAL Team Six, was intended to gather intelligence about the senior leadership of al-Qaeda in the Arabian Peninsula and its plotting efforts outside the region.

The U.S. military concluded Wednesday that the raid, in which at least 14 AQAP fighters were killed, also "likely killed" civilians, possibly including children.

"A team designated by the operational task force commander has concluded regrettably that civilian non-combatants were likely killed in the midst of a firefight during a raid in Yemen Jan. 29. Casualties may include children," read a statement from the U.S. Central Command.

However, a counterterrorism official familiar with the operation's details and after-action assessments told ABC News Thursday, "There definitely were civilian casualties."

Reprieve, an international human rights group that frequently represents victims of drone strikes and their families, said that as many as 23 civilians may have been killed in the raid.

"An attack on a village in Yemen ordered by President Trump on Sunday caused the death of a newborn baby, alongside as many as 23 civilians," Reprieve said in a press release.

Alice Gillham, the press and communications officer at Reprieve, told ABC News that the organization arrived at that figure from speaking to local human rights organizations, as well as people in the village.

Spicer insisted Thursday that the raid was successful despite allegations of civilian casualties.

"It's hard to ever call something a complete success when you have the loss of life or people injured. But ... it is a successful operation by all standards," Spicer said.

In outlining how the raid came about, Spicer said that Secretary of Defense James Mattis first conveyed his support for moving forward with the mission to the White House on Jan. 24. The president was briefed the following day by National Security Advisor Michael Flynn Michael Flynn on the recommendation of Mattis, Spicer said.

The president then had a dinner meeting with many of his top advisers in which the operation was laid out in great detail, according to Spicer. The president was in the White House during the raid, Spicer said, and remained in touch with the National Security Council and Mattis throughout the night.

"So he was kept apprised of the situation throughout the evening," Spicer said.

According to a U.S. official, an intercept indicated that someone within the vicinity of the al-Qaeda compound may have heard aircraft approaching.

Capt. Jeff Davis, a spokesman for the Pentagon, denied reports that the element of surprise may have been compromised. “We have no information to suggest that this was compromised," he said.

One Navy SEAL was also killed in the raid, which left three other SEALs wounded.

Davis said the U.S. Central Command is investigating whether civilians were killed in the raid.

ABC News' Katherine Faulders and Jordyn Phelps contributed to this report.

Editor's note: An earlier version of this story misstated the number of civilian deaths in the raid. Reprieve says it has accounted for 23 civilian deaths.