The Obama administration is preparing to announce as early as next week that it believes around 100 civilians have died in nearly 500 U.S. drone strikes since 2009, U.S. officials tell NBC News.

That is a far lower estimate than those of the three major independent groups that seek to track the secret operations in the Middle East, South Asia and Africa. The highest estimate among those groups puts civilian casualties from drones at over 1,000.

The disclosure, which is expected to cite an estimated range of civilian deaths lower and higher than 100, represents the latest attempt by the president to fulfill his promises to be more transparent about the controversial secret killing program he ramped up when he took office. Despite those vows, officials continue to release very little information about the targets and circumstances of each lethal strike.

Obama is expected to issue an executive order requiring annual disclosures of civilians killed in counter-terrorism strikes, officials say, a development first reported by the Daily Beast.

Human rights groups praised the move, but remain skeptical about the numbers.

“This is a big victory,” said Naureen Shah, who directs Amnesty International’s human rights program in Washington. However, she added, “It’s impossible to assess their claims without the administration acknowledging or denying the specific cases that we’ve put forward.”

U.S. officials have credited drone strikes carried out by the CIA and the military’s Joint Special Operations Command with putting al Qaeda on its heels. Officials have long said that Hellfire missiles fired from unmanned drones are far more precise than conventional bombing when it comes to targeting terrorists living among civilians.

The disparity in the civilian casualty numbers, however, is likely to fuel the debate about whether U.S. officials can be trusted to grade their own work based on evidence no one else can see.

It is not seriously disputed that U.S. targeted killing operations outside of active war zones have become less frequent and more discriminating in recent years. The main reason for that, officials say, was Obama’s decision in 2013 to impose rules that such attacks may only be carried out if there is a “near certainty” that civilians won’t be harmed.

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The Britain-based Bureau of investigative Journalism, which U.S. officials often privately criticize as biased against the U.S. government, counted one civilian casualty in three Pakistan strikes and none in 13 Yemen strikes so far in 2016.

But when it comes to the overall count since Obama took office, which includes a period from 2009 to 2011 when Obama authorized a flurry of CIA drone strikes in Pakistan, there is a stark disagreement.

The Long War Journal, a project of the right-leaning Foundation for Defense of Democracies think tank whose numbers tend to be the most favorable for U.S. policy-makers, tallied 207 civilian casualties since 2009 in 492 strikes in Pakistan and Yemen. That does not include strikes in Somalia and Libya, which the Obama administration includes in its count of around 100.

New America, a left-leaning Washington think tank, counted between 244 and 294 civilians killed in 547 attacks in Pakistan, Yemen and Somalia.

The Bureau of Investigative Journalism estimates that as many as 1068 civilians were killed in Pakistan, Yemen and Somalia, the vast majority since 2009.

Obama administration officials point out that those groups rely mainly on local media reports, which they argue are often distorted.

For example, current and former officials tell NBC News, Pakistan has on several occasions conducted its own airstrikes against militants and then attributed those attacks to CIA drones. Pakistani media reports based on those leaks then fuel the independent counts.

U. S. Defense Secretary Ash Carter addresses U.S. troops as he stands in front of a drone at the Incirlik Air Base near Adana, Turkey, Tuesday, Dec. 15, 2015. AP

Still, questions have long been raised about how the administration counts military-aged males killed in each strike, and what standard of evidence is used to label someone a militant.

For example, JSOC in 2013 carried out a strike in Yemen that killed 12 people who were deemed militants. But local officials said the strike hit a wedding party, and CIA analysts could not say with confidence that all the dead were combatants.

And after a CIA strike in 2011 killed 44 in Pakistan, CIA officials insisted the dead were all linked to the Taliban. But Pakistani officials said the agency had hit a meeting to settle a mining dispute, and that most of those killed were civilians.

In 2013, according to Amnesty, a strike in Pakistan killed a 68-year-old Pakistani grandmother named Mamana Bibi and 18 civilian laborers.

Whether the Obama administration’s civilian casualty report will address those and other disputed strikes is unclear.

Many of the alleged mistakes came during the early years of the Obama administration, when the CIA and JSOC expanded their use of so-called signature strikes –- attacks against groups of militants who fit the pattern of terrorists, but whose identities weren’t known. NBC News reported in 2013 on classified documents showing the CIA did not always know who it was killing.

There is also a drone campaign ongoing against ISIS in Iraq and Syria, but that effort is part of a larger conventional bombing campaign operating under the less stringent rules for military targeting that does not apply the “near certainty” standard. The U.S. military, which releases aggregate numbers of strikes, refuses to say which attacks came from unmanned platforms.

The military drone program is technically separate from the one operated by the CIA, but it relies on intelligence gathered from unarmed CIA drones, as well as on human sources, NSA intercepts, and other intelligence. Obama has been shifting the bulk of lethal drone attacks from the CIA to the military, but the CIA retains the capability for cases when the host country will not allow a U.S. military presence.

The level of civilian casualties from that effort is also in dispute. The military counts 41 total, while the website Airwars says a minimum of 1,323 civilians have been killed by coalition action in Iraq and Syria.

The White House declined to comment.