WASHINGTON — A US Marine sergeant has been given an "other than honorable" discharge after posting remarks critical of President Barack Obama on Facebook, the Marine Corps announced Wednesday.

Gary Stein, 26, a nine-year veteran, has been "separated from the Marine Corps" for his "misconduct," the Marines said in a statement.

The Marines added that an other than honorable discharge is given when the "basis for separation is the commission of a serious offense which is a significant departure from the conduct expected of a Marine."

The statement said those receiving an other than honorable discharge "are automatically reduced to pay grade E-3" -- that of a lance corporal.

Stein posted comments on Facebook and other websites calling Obama a coward and "the economic and religious enemy," a Marine Corps board was told during a hearing earlier this month.

Stein had urged Obama's defeat in the November election, writing "screw Obama" in one posting, and had founded a website called Armed Forces Tea Party, apparently in support of the ultra-conservative Tea Party movement.

On one site he sold bumper stickers reading "NOBAMA 2012."

As president, Obama is the commander-in-chief of US armed forces.

Stein's lawyers had argued that as the comments were made off-duty, they are protected under constitutional guarantees of freedom of expression, saying the Marine Corps's own rules on the matter are vague.

They argued that restricting Marines from participating in political discussions essentially reduced them to second-class citizens.

Stein, who served in Iraq, had been assigned to scheduling rifle ranges at Camp Pendleton. His enlistment was set to end in July, and he had hoped to reenlist.