Egypt ignored paperwork that could have secured the release of Mustafa Kassem who died in prison at the beginning of January, reports NBC News.
Egypt told the US that Kassem was eligible for release if he denounced his Egyptian citizenship and he had submitted the papers to do so six months before he died.
"I'm extremely troubled that the Egyptian government chose to sit on the paperwork to release Mustafa Kassem for months, essentially sealing his fate to die in their prisons," said Democratic Senator Chris Murphy in a statement.
Kassem was arrested in 2013 on terror-related charges whilst on his way to exchange money at a shopping mall. He was in Egypt visiting family.
In January he became the first American citizen to die inside Egypt's prisons. He had been kept in pre-trial detention in Egypt's notorious Tora Prison for over five years before being sentenced in a mass trial.
Kassem, who was a New York taxi driver, had diabetes and a heart ailment and died of heart failure after being denied adequate medical care.
He had been on hunger strike protesting against his unfair trial since September 2019 and had recently resorted to a thirst strike.
WATCH: Leaked audio from Egypt prison: 'Someone is sick guard'
Last week, a leaked audio recording from Tora Prison captured detainees banging on the doors of their cells calling a prison guard to save a prisoner who is in a critical condition.
The recording highlights the desperate plight of medical neglect inside Egypt's prisons, where cellmates often plead for prison authorities to help sick prisoners and are ignored.
In December, the US Secretary of State Mike Pompeo raised the issue of Mustafa Kassem with his Egyptian counterpart Sameh Shoukry at a meeting in Washington.
Kassem had written letters to US President Donald Trump and Vice President Mike Pence pleading them to intervene.
Washington is Egypt's closest Western ally and a top aid donor. Kassem was convicted around the same time Pompeo authorised $1.3 billion of US military aid to Egypt.
Politicians and activists have consistently urged the US to suspend aid to Egypt and use it as leverage to force the North African country to respect human rights.
Rights groups have documented the death of 917 people in custody between June 2013 and November 2019, 677 from medical neglect and 136 from torture.
The Francophone Association for Human Rights (AFDH) are calling for urgent intervention to save political prisoners from the same fate as Kassem on the grounds that overcrowding and medical negligence are posing an "imminent threat to prisoner's lives".