After escalating one of the most lethal covert operations in U.S. history,
Human rights groups immediately challenged the estimate and the amount of transparency from the administration, saying both were too limited.
Monitoring organizations estimate the number of civilians killed in U.S. strikes ranges from 200 to more than 1,000.
Administration officials defended their figure, but admitted they often do not know for sure who is among the dead after a strike.
"We acknowledge these assessments may be imperfect," said a senior administration official, who briefed reporters Friday on condition of anonymity.
Determining exact figures is difficult because drone strikes frequently take place in "non-permissive environments," the official said.
The administration said that the strikes have also killed 2,372 to 2,581 people it classified as combatants. The strikes almost all have taken place in poor, isolated countries where outside monitoring is nearly impossible.
Along with the casualty estimate, Obama issued an executive order that calls for protective measures for civilians and requires future administrations to release an estimate of civilian casualties on May 1 of each year.
The administration timed the release of its report in a manner likely to minimize attention – the Friday before the Fourth of July weekend. The estimate provided only an aggregate number of deaths over all seven years without breaking it down by country, which makes analysis difficult.
"The disclosure is a step in a positive direction, but aggregate numbers are close to useless," said Jameel Jaffer, the deputy legal director of the American Civil Liberties Union, which has sued the administration for greater transparency about the drone program.
"I should also say it's easy to promise transparency on behalf of the next administration," Jaffer said. "The next president can revoke this order with a stroke of a pen."
The administration also plans to release documents soon that would shed light on the legal rationale behind the government's claims for its authority to remotely kill militants based on top-secret evidence in countries where the U.S. has not declared war: Yemen, Pakistan, Libya and Somalia.
Known as the Presidential Policy Guidance and nicknamed the playbook, the document sets the legal standards that the government has followed in many strikes since 2013.
The ACLU sued the administration to obtain access to the policy guidance. Its release has been delayed by discussions between the court and the administration over redacting information.
Until now, most matters related to the drone program, run by the CIA and the U.S. military's secretive Joint Special Operations Command, have been hidden from public view.
The administration, in most cases, had refused to acknowledge the existence of the program or answer questions about how decisions were made about who is targeted.
Obama promised greater transparency and oversight on drone strikes in a May 2013 speech at National Defense University. The administration has provided few details since then about how the drone program is structured, what legal restrictions apply, and what oversight or accountability is involved.
Naureen Shah, director of Amnesty International USA's Security and Human Rights Program, applauded the fact that Obama had taken a step toward transparency but added that the administration has a long way to go.
"Without information on the administration's definitions and legal standards for these strikes, any meaningful assessment of the numbers will be incomplete," she said.
"This is not the end of the public conversation on U.S. drone strikes, but just the beginning."
The shadowy counterterrorism campaign has revolutionized warfare. Armed drones, which typically are piloted from Creech Air Force Base in Nevada or CIA officers in Northern Virginia, can watch a target for weeks or months at a time.
Once used to target specific individuals, whom the administration termed "high value targets," the strikes now mainly kill lower-level militants whose names are often not even known by the government.
The limits of U.S. intelligence and remote-controlled air attacks have been visible for years. In April 2015, for example, Obama announced that a CIA drone strike that January on an
Hundreds of hours of aerial surveillance, communications intercepts and other intelligence had failed to spot signs of the hostages, officials said.
At least eight Americans have been killed by drone attacks. Only one, Anwar Awlaki, an Al Qaeda leader who was based in Yemen, was specifically targeted. Among the other American citizens killed were Samir Khan, an Al Qaeda propagandist who grew up in New York and was killed alongside Awlaki, and Awlaki's 16-year-old son, Abdulrahman, who was born in Denver and killed in Yemen two weeks after his father.
The administration hasn't commented on those deaths.
"Despite our best efforts to ensure to a near-certainty that no non-combatants will be killed or injured, sometimes strikes do result in harm to the innocent," said Adam B. Schiff (D-Burbank), the top Democrat on the House Intelligence Committee. "It is important that we continue to acknowledge those incidents, learn from them, hold ourselves accountable and be as transparent as possible."
3:48 p.m.: This article was updated with additional information.
2:20 p.m.: This article was updated with additional information from the administration's report and reaction.