The Trump administration's lethal strikes on alleged "narco-trafficking" vessels at sea could be considered crimes against humanity that violate international, maritime and humanitarian law, according to a United Nations report.
Since September last year, the United States military has launched air strikes on at least 68 vessels in the Pacific Ocean and Caribbean Sea, killing at least 223 people.
Donald Trump says the operation, known as "Southern Spear" is necessary because the US is in an armed conflict with Latin American drug gangs transporting fatal drugs to America.
The US president has also defended it as "self-defence" against groups such as the Venezuelan Tren de Aragua and Cartel de los Soles gangs, designated as Foreign Terrorist Organisations (FTOs).
The strikes began amid an escalation in tensions that culminated in the "capture" of former Venezuelan President Nicolás Maduro by US forces in a covert night-time military operation.
In a briefing note prepared for the UN Human Rights Council, Special Rapporteur Ben Saul said there is no legal justification supporting Mr Trump's perspective.
Mr Saul found there was "growing evidence" showing the military operation had not reduced the volume of illicit drugs entering the US.
After discussions in Colombia, newly-elected President Abelardo De La Espriella announced a plan to grow cooperation with the US, which has already seen American forces contribute to Colombian strikes and raids against drug cartels in the country.
On September 9, Mr Rubio confirmed he would seek $US45 million in funding for Ecuador to crack down on drug trafficking, and the US and Ecuadorian militaries have launched joint strikes on vessels off the country's shores.