A group of nongovernmental organisations called on the Trump administration to clarify its policy on drone use, saying they are concerned about reported changes to US rules and a lack of transparency in the decision-making process.
"We are deeply concerned that the reported new policy, combined with this administration's reported dramatic increase in lethal operations in Yemen and Somalia, will add to an increase in unlawful killings and in civilian casualties," a joint statement said.
The organisations include Amnesty International, the US-based Center for Constitutional Rights, Human Rights Watch, the ACLU and others.
President Donald Trump signed the 2018 National Defense Authorization Act in December. The act funds the US military but also requires Trump to make known to Congress any changes to previous drone policies by March 12.
The statement detailed alleged changes in policy, which are reported to have been made to Obama-era guidelines but have not been confirmed by the current government.
The Trump administration, embroiled in scandals and resignations, has not signalled it will make changes to drone policy known.
The reported changes include a relaxing of the "imminent threat requirement", which means the US may select targets outside of armed conflict, the standard of requiring "near certainty" that the target is present, and an increased role for the CIA.
Daniel Mahanty, director of the US programme for the Center for Civilians in Conflict, told Al Jazeera these "changes, and the fact that the administration refuses to make them public, should concern Americans and the many countries upon which the US depends for cooperation and support".
Furthermore, the relaxations "increase the risk that more civilians will lose their lives or livelihoods with very little recourse to pursue any meaningful remedy", Mahanty said.
According to Airwars - a watchdog group that tracks "airpower-dominated international military actions" - there was a nearly 50 percent increase in drone attacks in Iraq and Syria, while civilian deaths rose roughly 215 percent from 2016 to 2017.
In Somalia, where American drones are active, the US killed more than 200 people in 2017, according to the Bureau of Investigative Journalism.
The US' latest drone attack took place in Yemen on Tuesday. The attack killed four people said to be linked to al-Qaeda in Hadramout province, China's Xinhua news agency reported.
Yemen has been the epicentre for US drone raids since the Obama administration. Trump has continued that policy, rights group say.
"Last year alone, President Trump carried out more than three times as many strikes in Yemen as Obama, and authorised two raids that killed almost a dozen children and a Navy SEAL," Jennifer Gibson, head of the assassinations programme at Reprieve - one of the signatories of the joint statement, told Al Jazeera.
While watchdog groups try to keep track of drone attacks, it is often difficult to confirm circumstances or death tolls in war-torn areas.
US armed forces and intelligence services have been accused of hiding details and doctoring numbers to make drone attacks appear more accurate.
Former CIA director John Brennan said in June 2011 "there hasn't been a single collateral death" in Pakistan for more than a year. The claim was widely disputed.
Drone policy, including who and where the president can kill, "should not remain hidden in the shadows", said Gibson.