A leading US medical journal on Wednesday hit out at the powerful American gun lobby for opposing the nomination for the post of top doctor, calling it a new form of "political blackmail."

At issue is the nomination to the post of of a Harvard medical school physician named Vivek Murthy, whose parents were born in India.

Murthy "has lived the American dream," said the editorial in the New England Journal of Medicine, noting his role in expanding HIV education, broadening access to healthcare and fighting childhood obesity.

His nomination awaits a vote in the US Senate, but that vote may be postponed or his candidacy withdrawn, amid reports that as many as 10 Senate Democrats would vote against him, enough to keep him out of the post.

The National Rifle Association has sent letters to lawmakers and to members over the past two months, urging them to oppose Murthy based on his views on guns.

"Dr. Murthy's record of political activism in support of radical gun control measures raises significant concerns about his ability to objectively examine issues pertinent to America's 100 million firearm owners," said one NRA letter to lawmakers, sent to AFP by the NRA press office.

A separate email alert to NRA members described Murthy as someone who agrees with President Barack Obama's "radical anti-gun agenda" and who has "advocated on many occasions for the banning of lawfully owned firearms."

"It's clear that Dr. Murthy would be a prescription for disaster for America's law-abiding gun owners," the email said, urging NRA members to contact their senators to express their opposition.

The editors of the New England Journal of Medicine said Murthy has stood for "reasonable and mainstream forms of gun regulation, including an assault weapons ban, a limit on ammunition sales, and required safety training."

These views are "unsurprising" given the more than 30,000 firearm deaths in the United States each year, the editorial said.

It also pointed out that Murthy has said that if confirmed, his principal focus would be on preventing obesity in America.

"This is the first time that the NRA has flexed its political muscle over the appointment of a surgeon general," the editors wrote.

"By obstructing the president's nomination of Vivek Murthy as surgeon general, the NRA is taking its single-issue political blackmail to a new level."

The authors concluded by calling on US senators to confront the NRA and vote according to their conscience.

"Dr. Murthy is an accomplished physician, policymaker, leader and entrepreneur. He deserves the president's continued backing and should be confirmed."

Journal information: New England Journal of Medicine