At the behest of the director of national intelligence, US senators have removed a provision from a major intelligence bill that would require the president to publicly disclose information about drone strikes and their victims.

The bill authorizing intelligence operations in fiscal 2014 passed out of the Senate intelligence committee in November, and it originally required the president to issue an annual public report clarifying the total number of “combatants” and “noncombatant civilians” killed or injured by drone strikes in the previous year. It did not require the White House to disclose the total number of strikes worldwide.

But the Guardian has confirmed that Senate leaders have removed the language as they prepare to bring the bill to the floor for a vote, after the director of national intelligence, James Clapper, assured them in a recent letter that the Obama administration was looking for its own ways to disclose more about its highly controversial drone strikes.

“The executive branch is currently exploring ways in which it can provide the American people more information about the United States’ use of force outside areas of active hostilities,” Clapper wrote to the leaders of the Senate committee, Democrat Dianne Feinstein of California and Republican Saxby Chambliss of Georgia, on 18 April.

“To be meaningful to the public, any report including the information described above would require context and be drafted carefully so as to protect against the disclosure of intelligence sources and methods or other classified information. … We are confident we can find a reporting structure that provides the American people additional information to inform their understanding of important government operations to protect our nation, while preserving the ability to continue those operations,” Clapper continued.

Another provision, which would require alternative intelligence analysis, as well as commensurate congressional notification should an intelligence agency consider legal action against a US citizen, has been moved to a classified annex of the bill.

Lawmakers were said to remove the provision in hopes of passing the full bill in the coming weeks.

The removal of the drone transparency requirement is the latest in a pattern by legislators to preserve the status quo surrounding the strikes.

In January, the Senate obstructed an effort by the Obama administration that would have removed the CIA from drone operations and given responsibility for them to the Defense Department, which conducts parallel and occasionally complementary drone strikes.

Feinstein, the chairwoman of the Senate intelligence committee, has recently been locked in a different sort of declassification battle: an effort to compel the Obama administration to declassify aspects of a major report into the CIA’s post-9/11 torture of terrorism detainees, completed by her committee.

Senate intelligence committee chair Senator Dianne Feinstein. Photograph: Molly Riley/AP Photograph: Molly Riley/AP

But Feinstein has long been a defender of the CIA’s drone strikes. During a February 2013 confirmation hearing for CIA Director John Brennan, Feinstein stated that the CIA’s targeting procedures kills only “single digits” of civilians annually, an assertion that cannot be independently confirmed because of the official secrecy surrounding the strikes.

The sharing of even basic information about drone strikes has run into a wall of official secrecy. Several independent groups attempt to track the numbers of people killed in the strikes, but no official US confirmation has been possible. Word of the strikes usually arises from news accounts in their places of occurrence, such as Yemen or Pakistan.

The aftermath of an alleged US drone attack in Yemen's al-Bayda province. Photograph: Stringer/EPA Photograph: Stringer/EPA

Independent observers, including the United Nations special rapporteur on counterterrorism, have repeatedly called on Washington to increase transparency around the lethal operations. An April paper by Larry Lewis of the CNA Corporation, who has close ties with the US military, urged the administration to conduct and appropriately disclose assessments of civilian casualties from drone strikes, to help “ensure that official US statements reflect operational realities, helping to guard the credibility and reputation of the US”.

Thus far those efforts have largely floundered. In May 2013, Obama announced that he wanted to restrict but not eliminate drone strikes, whose use he defended as a necessary component of counterterrorism. Obama confirmed that civilians have died from drone strikes, an effect that he said “will haunt us as long as we live”, but he did not disclose how many cases of errant missile or mistaken targeting strikes have occurred.

In public testimony, leaders of the intelligence agencies have not rejected the transparency provisions. During a February House hearing, Brennan called a proposal from congressman Adam Schiff, a California Democrat, to disclose the annual numbers of fighters and civilians killed by drones “certainly a worthwhile recommendation”.

Schiff and a North Carolina Republican, Walter Jones, introduced a bill this month to compel the drone casualty totals and combatant breakdowns, which Schiff termed a “modest, but important, measure of transparency and oversight regarding the use of drones”.

The previous February, Senator Lindsey Graham, a South Carolina Republican and member of the armed services committee, was quoted tallying the deaths caused by drone strikes over the past decade at 4,700 people. Graham did not disclose either the basis for his estimate or a breakdown of how many civilians the total includes.

US drones strikes are declining worldwide, according to statistics gathered and analyzed by the Council on Foreign Relations. In 2013, there were approximately 55 strikes in Yemen, Pakistan and Somalia, killing as many as 271 people, down from the 92 strikes that killed up to 532 people in 2012. While drone strikes in Pakistan are sharply down in 2014, a recent offensive aimed at Yemen’s al-Qaida affiliate and including US drone strikes left about 55 people dead last week.

Human rights activists reacted with disappointment to the removal of the transparency requirement.

“How many people have to die for Congress to take even a small step toward transparency? It's stunning that after all these years we still don't know how many people the Obama administration has killed with drones,” said Zeke Johnson, the director of Amnesty International’s security and human rights program.