The US government has not fully investigated its own role in perpetuating human rights abuses in Yemen, according to a congressional watchdog report that offered a damning assessment of both the Trump and Biden administrations’ commitment to tracking violations of humanitarian law.

A report by the Government Accountability Office, which examined US weapons sales to the Saudi-led coalition in Yemen, also raised serious doubts about one of Joe Biden’s first foreign policy as president, when he announced that his administration was ending US support for Saudi offensive operations in Yemen.

At the time, in February 2021, the move was seen as an attempt to show the world that the US would no longer be an unquestioning ally to its allies in the Gulf.

But the GAO found that the Biden administration’s move to classify weapons as offensive or defensive was largely meaningless. When asked by the GAO how they had distinguished between equipment used for defensive purposes and offensive purposes, state department officials “could not provide a definition for equipment that is defensive in nature”.

The GAO report added: “State officials said they consider the threats posed to Saudi Arabia’s borders and infrastructure when deciding which weapons are ‘offensive’ and which are ‘defensive’.”

A spokesperson for the White House national security council did not immediately return a request for comment.

The report’s examination of nearly $60bn in US weapons sales to the Saudi-led coalition – from a period spanning 2015 to 2021 – is the second time a watchdog has attempted to investigate the US’s own culpability in contributing to violation of humanitarian laws in the Yemen conflict. In August 2020, a state department inspector general found that the department was failing to take measures to reduce civilian deaths.

The GAO found that both the state department and the Department of Defense had made “some efforts” to understand civilian harm and the use of US-origin weapons in Yemen. But it also found no evidence that the state department had ever investigated any allegations that US equipment transferred to Saudi Arabia and the UAE had ever been used for unauthorised purposes or against anything other than “legitimate targets”.

The troubling findings come days after the White House confirmed that Biden will visit Riyadh next month, in what is widely seen as an effort to persuade the kingdom to increase oil output and ease price pressure for consumers.

Human rights advocates who have supported Biden’s decision – so far – to try to personally alienate Saudi’s de facto leader, Mohammed bin Salman, have called the visit a “betrayal” of Biden campaign promise to turn Saudi into a pariah.

The UN has called the Saudi-led war in Yemen one of the world’s worst humanitarian crises, affecting an estimated 21 million people.

The GAO reported that the US DoD had made some efforts to train Saudi officials to mitigate civilian casualties and adhere to international humanitarian law. But the DoD has never “fully measured” the extent to which its advising and training has helped to facilitate “civilian harm reduction” in Yemen.

The GAO also said that it had been told by the state department that officials there could not locate three so-called “country team” assessments to the UAE, which would have included critical information and how the US has evaluated weapons sales requests. 

The report said that, according to DoD policy, the assessments must also include the “potential for misuse of the defense articles in question” and what “additional training or support, if any, is necessary to reduce the risk that the recipient will inadvertently cause civilian harm during operations”.

GAO requested the assessments in September and were told this month that they have been located and would be provided to GAO once clearance was obtained.