Pentagon officials said Wednesday that about one-third of the US military are declining to receive the Covid-19 vaccine, despite significant coronavirus infection levels in the forces.

Major General Jeff Taliaferro revealed the high refusal rate in Congressional hearing, as the US Defense Department continues to classify covid vaccines as optional because they have yet to receive full approval from the Federal Drug Administration.

"Acceptance rates are somewhere in the two-thirds territory," said Taliaferro, stressing that the figure is based on "very early data."

Pentagon Spokesman John Kirby said that there was no detailed military-wide data on vaccinations, but said more than 916,500 had been administered so far.

Kirby said the level of refusal is on par with that of the general population, where the vaccine has not been offered nearly as widely. "We in the military basically mirror the acceptance rates of American society," Kirby told reporters.

The government has tapped the military and National Guard to help vaccinate the general public people. Kirby said that by the end of this week, more than one million members of the military will have received vaccine shots.

The Pentagon makes most standard vaccinations mandatory for military personnel. But because the covid vaccines have only been approved on an emergency basis, they cannot be forced on people, Kirby said. "There is a real limit, legally, that we have, to make it mandatory for our troops and their families."

He noted that Secretary of Defense Lloyd Austin has received the vaccine.

"What the secretary wants is for the men and women of the department to make the best and most informed decision for them and their health and the health of their families," Kirby said.