Washington (CNN) The U.S. has adopted a unique Israeli battlefield tactic in its fight against ISIS: exploding a missile above a building to warn civilians inside that it's about to be bombed.

Israeli forces have widely used the so-called knock-on-the-roof operations in Gaza attacks in recent years to try to get civilians out before they are hit.

The first public revelation of the U.S. using a "knock operation" came Tuesday at a press briefing by Air Force Maj. Gen. Peter E. Gersten, deputy commander for operations and intelligence for the anti-ISIS Operation Inherent Resolve.

Iraqi government forces patrol in southern Falluja, Iraq, on June 10, 2016. In late June, a senior Iraqi general announced that the battle to reclaim Falluja from ISIS had been won.

A boy walks past bloodstains and debris at a cafe in Balad, Iraq, that was attacked by ISIS gunmen on May 13, 2016. Twenty people were killed.

A boy walks past bloodstains and debris at a cafe in Balad, Iraq, that was attacked by ISIS gunmen on May 13, 2016. Twenty people were killed.

Two wounded women sit in the airport in Brussels, Belgium, after two explosions rocked the facility on March 22, 2016. A subway station in the city was also targeted in terrorist attacks that killed at least 30 people and injured hundreds more. Investigators say the suspects belonged to the same ISIS network that was behind the Paris terror attacks in November.

Members of Iraq's elite counterterrorism unit celebrate December 28, 2015, after recapturing the city of Ramadi. The city fell to ISIS in May 2015.

Law enforcement officers search a residential area in San Bernardino, California, after a mass shooting killed at least 14 people and injured 21 on December 2, 2015. The shooters -- Syed Rizwan Farook and his wife, Tashfeen Malik -- were fatally shot in a gunbattle with police hours after the initial incident. The couple supported ISIS and had been planning the attack for some time, investigators said.

Spectators at the Stade de France in Paris run onto the soccer field after explosions were heard outside the stadium on November 13, 2015. Three teams of gun-wielding ISIS militants hit six locations around the city, killing at least 129 people and wounding hundreds.

Two women hold hands after an explosion in Suruc, Turkey, on July 20, 2015. The blast occurred at the Amara Cultural Park, where a group was calling for help to rebuild the Syrian city of Kobani, CNN Turk reported. At least 32 people were killed and at least 100 were wounded in the bombing. Turkish authorities said they believed ISIS was involved in the explosion.

A man inspects the aftermath of a car bombing in Khan Bani Saad, Iraq, on July 18, 2015. A suicide bomber with an ice truck, promising cheap relief from the scorching summer heat, lured more than 100 people to their deaths. ISIS claimed responsibility on Twitter.

ISIS also claimed responsibility for what it called a suicide bombing at the Al-Sadiq mosque in Kuwait City on June 26, 2015. At least 27 people were killed and at least 227 were wounded, state media reported at the time. The bombing came on the same day as the attack on the Tunisian beach.

Dead bodies lie near a beachside hotel in Sousse, Tunisia, after a gunman opened fire on June 26, 2015. ISIS claimed responsibility for the attack, which killed at least 38 people and wounded at least 36 others, many of them Western tourists. Two U.S. officials said they believed the attack might have been inspired by ISIS but not directed by it.

In May 2015, ISIS took control of Palmyra, Syria, and began to destroy ancient ruins and artifacts. The Temple of Bel is seen here after Syrian forces reclaimed the city in March 2016. ISIS has also destroyed other cultural sites in Syria and Iraq.

An Iraqi soldier searches for ISIS fighters in Tikrit on March 30, 2015. Iraqi forces retook the city after it had been in ISIS control since June 2014.

In March 2015, ISIS released video and images of a man being thrown off a rooftop in Raqqa, Syria. In the last photograph, the man is seen face down, surrounded by a small crowd of men carrying weapons and rocks. The caption reads "stoned to death." The victim was brutally killed because he was accused of being gay.

In February 2015, British newspapers report the identity of "Jihadi John," the disguised man with a British accent who had appeared in ISIS videos executing Western hostages. The militant was identified as Mohammed Emwazi, a Kuwaiti-born Londoner. On November 12, 2015, the Pentagon announced that Emwazi was in a vehicle hit by a drone strike. ISIS later confirmed his death.

Safi al-Kasasbeh, right, receives condolences from tribal leaders at his home village near Karak, Jordan, on February 4, 2015. Al-Kasasbeh's son, Jordanian pilot Moath al-Kasasbeh, was burned alive in a video that was released by ISIS militants. Jordan is one of a handful of Middle Eastern nations taking part in the U.S.-led military coalition against ISIS.

A Kurdish marksman stands atop a building as he looks at the destroyed Syrian town of Kobani on January 30, 2015. After four months of fighting, Peshmerga forces liberated the city from the grip of ISIS.

ISIS militants stand near the site of an airstrike near the Turkey-Syria border on October 23, 2014. The United States and several Arab nations began bombing ISIS targets in Syria to take out the group's ability to command, train and resupply its fighters.

On August 19, 2014, American journalist James Foley was decapitated by ISIS militants in a video posted on YouTube. A month later, they released videos showing the executions of American journalist Steven Sotloff and British aid worker David Haines.

Aziza Hamid, a 15-year-old Iraqi girl, cries for her father while she and other Yazidi people are flown to safety after a dramatic rescue operation at Iraq's Mount Sinjar on August 11, 2014. A CNN crew was on the flight, which took diapers, milk, water and food to the site where as many as 70,000 people were trapped by ISIS. Only a few of them were able to fly back on the helicopter with the Iraqi Air Force and Kurdish Peshmerga fighters.

ISIS fighters parade down an Iraqi street in this image released by the group in July 2014.

ISIS fighters parade down an Iraqi street in this image released by the group in July 2014.

Traffic from Mosul lines up at a checkpoint in Kalak, Iraq, on June 14, 2014. Thousands of people fled Mosul after it was overrun by ISIS.

Kurdish Peshmerga fighters fire missiles during clashes with ISIS in Jalawla, Iraq, on June 14, 2014. That month, ISIS took control of Mosul and Tikrit, two major cities in northern Iraq.

Kurdish Peshmerga fighters fire missiles during clashes with ISIS in Jalawla, Iraq, on June 14, 2014. That month, ISIS took control of Mosul and Tikrit, two major cities in northern Iraq.

The ISIS militant group -- led by Abu Bakr al-Baghdadi, pictured -- began as a splinter group of al Qaeda. Its aim is to create an Islamic state, or caliphate, across Iraq and Syria. It is implementing Sharia law, rooted in eighth-century Islam, to establish a society that mirrors the region's ancient past. It is known for killing dozens of people at a time and carrying out public executions.

People flee the scene of a terror attack at Istanbul's Ataturk airport on June 29. Turkish officials have strong evidence that ISIS leadership was involved in the planning of the attack, a senior government source told CNN. Officials believe the men -- identified by state media as being from Russia, Uzbekistan and Kyrgyzstan -- entered Turkey from the ISIS stronghold of Raqqa in Syria, bringing with them the suicide vests and bombs used in the attack, the source said.

Gersten described a strike against an ISIS financial storage center on April 5 in southern Mosul, Iraq. The U.S. had been closely watching the house of an ISIS finance operative, or "finance emir" in the words of Gersten.

"He was the major distributor of funds to Daesh fighters," Gersten said, using another name for ISIS. "We watched him come and go from his house, we watched his supplies, we watched the security that was involved in it. And we also watched occasionally a female and her children in and out of the quarters."

Using reconnaissance aircraft and other intelligence assets to keep watch, the U.S. then began to formulate a plan, Gersten said, to get women, children and other civilians out of the building.

"We went as far as actually to put a Hellfire on top of the building and air-burst it so it wouldn't destroy the building, simply knock on the roof to ensure that she and the children were out of the building," he recounted. "And then we proceeded with our operations."

Gersten acknowledged the Israeli influence, saying, "That's exactly where we took the tactics and technique and procedure from."

Gersten did not indicate that the Israeli military had formally briefed U.S. commanders on how to do knock operations.

But he noted, "We've certainly watched and observed their procedure. As we formulated the way to get the civilians out of the house, this was brought forward from one of our experts."

Gersten said that leaflets were also dropped to warn of a pending attack. In some Israeli operations, phone calls have been made to houses about to be hit as well.

Israel, however, has come under fire from human rights groups for use of the tactic.

"There is no way that firing a missile at a civilian home can constitute an effective 'warning,'" said Philip Luther, Middle East and North Africa Director at Amnesty International, about the Israeli practice in 2014. "Amnesty International has documented cases of civilians killed or injured by such missiles in previous Israeli military operations on the Gaza Strip."

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Human rights groups in Gaza agreed.

"The sending of a missile cannot be considered a warning. It is the targeting of civilians with a weapon, regardless of how small, and it is a violation of the Geneva conventions," said Mahmoud Abu Rahma of the Al Mezan Center for Human Rights, also referring to Israel's actions.

"Imagine you are in Gaza and there are airstrikes everywhere, and many families are in the bottom floor of their home," Abu Rahma added. "Families miss the sound of the 'warning' missile because it sounds like just another explosion."

The U.N. weighed in on the Israeli tactic, too, finding in a 2015 report that, "In a number of incidents examined, the concerned persons either did not understand that their house had been the subject of a 'roof-knock,' or the time given for evacuation between the warning and the actual strike was insufficient," pointing to an incident in which several children died after being given just a few minutes to evacuate at a time when most were sleeping.

"'Roof knocks' cannot be considered an effective warning given the confusion they often cause to building residents and the short time allowed to evacuate before the actual strike," the U.N. said.

It is not clear how much time the U.S. provided between the knock operation earlier in April and the actual strike. But initially the U.S. believed that the approach had worked to save the woman whom the U.S. had observed inside the building.

Despite the fact that "the men that were in that building -- multiple men -- literally trampled over her to get out of that building," according to Gersten, she was able to get out herself.

He continued, "We watched her and observed her leaving the building. And she cleared the building, and we began to process the strike."

But then, he said, she ran back in the building.

It was "very difficult for us to watch, and it was within the final seconds of the actual impact," Gersten recalled.

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There is video of the entire incident but it's unlikely to be released by the Pentagon because it shows a civilian being killed, according to a defense official.

The U.S. has seen no evidence the finance official has re-emerged and believes he is likely dead. Gersten did not further identify the man or the other ISIS members or civilians killed in the incident.

In his press briefing, Gersten emphasized that ISIS is suffering from morale problems among its fighters, in part due to the shortage of cash after more than a dozen airstrikes against money centers. He noted that the number of foreign fighters coming into Syria and Iraq has now dropped to about 200 a month compared to more than 1,500 a month a year ago, though that may be due to several reasons including morale and stronger border controls.

The U.S. is also putting a long-range artillery system in southern Turkey to conduct more strikes against ISIS targets in Syria, Gersten said.