English grammar books say to put "an" before vowels. However, "an united" just doesn't sound right <img class='emoticon' style='Width:19px;Height:19px;' data-delaysrc='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/2.gif' src='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/2.gif' alt='Emotion: big smile'/>.