A leading nursing association is urging the US military not to punish a navy nurse who has refused to forcibly feed Guantánamo detainees on hunger strike to protest their confinement without charge.

In letters the American Nurses Association made public on Wednesday, the organization of 3.1 million registered nurses asked defense secretary Chuck Hagel and the chief of naval nursing to spare the anonymous Guantánamo-based nurse any disciplinary measure, as the nurses’ professional code of ethics enshrines a right to “make an independent judgment about whether he or she should participate in this or any other activity”.

“A nurse’s primary commitment is to the patient,” reads the letter, dated 17 October and first reported by the Miami Herald, which in July broke the story that a Guantánamo nurse, apparently for the first time, refused to participate in the force feedings.

“It is incumbent on all leadership to recognize the code of ethics under which nurses and other professionals must practice,” American Nurses Association president Pamela Cipriano said in a Wednesday briefing for reporters.

The nurse, a navy officer, has not been identified. His lawyer, Ron Meister, said that the nurse preferred to conceal his identity until the “extremely serious” charges against him were resolved.

At issue is a looming decision by the navy’s chief of personnel to bring disciplinary charges before a three-officer board. The nurse, who Meister said has served in the navy for 18 years, could be discharged and lose his benefits and pension.

Meister said that at some point during the nurse’s tour on the Guantánamo medical staff, he had administered the force-feedings – conducted by inserting a tube through a detainee’s nostril and into his stomach – but came to see them as unethical, primarily owing to the detainees’ refusal to consent.

Meister said the navy risked sending a message to other military nurses that refusing to administer the force-feedings “could jeopardize their careers”.

In October, lawyers for a Syrian detainee on hunger strike, Abu Wa’el Dhiab, contended that the force-feedings were not only administered painfully, but were also not a strict medical necessity. Dhiab’s lawyers argued that the feedings were instead a military operation to break the hunger strikes.

Testimony in the case, introduced by the Department of Justice, indicated a Guantánamo policy of administering the feedings when a detainee who refused to eat had reached 85 percent of his “ideal body weight”, even though US officials including President Obama have described the feedings as necessary to prevent a detainee’s suicide.

The judge in the case, federal district judge Gladys Kessler, declined on 7 November to stop the force-feedings, but has previously described the feedings as painful and degrading.

The nurse’s treatment is the latest clash between a professional medical board and the military at Guantánamo. Elements within the American Psychological Association have pressed the board to rebuke its members for cooperation with torturous interrogations at Guantánamo and beyond.

While the association quietly absolved an army reserve major and psychologist at Guantánamo in January, its resistance to self-inquiry about compliance with torture buckled after reports of a posthumous behavioral-researcher whistleblower in James Risen’s recent book Pay Any Price.

The navy nurse “should be allowed to recuse himself without consequence”, said Naval War College professor Albert Shimkus, a retired navy captain and former Guantánamo surgeon. “That’s the essence of what we believe to be appropriate.”