A Vietnam vet is suing the head of a national business group that advises the White House on gay and lesbian issues for allegedly assaulting him at a Times Square hotel last year.

Michael McDonnell, 66, was visiting from Pennsylvania and was near an elevator at the W Hotel when National Gay and Lesbian Chamber of Commerce President Justin Nelson attacked him “without any forewarning, notice or justification,” according to his $5 million Manhattan Criminal Court suit.

Nelson, 42, pleaded guilty to disorderly conduct.

A rep for Nelson said, “The NGLCC . . . looks forward to Mr. Nelson being vindicated for defending himself during a homophobic incident.”

He declined to elaborate.

McDonnell’s attorney, Joel Silberman, said his client “unequivocally denies” making any anti-gay remarks.