barack_obama.jpgWASHINGTON (AP) _ President Barack Obama says Virginia's governor made “an unacceptable omission'' when he proclaimed April Confederate History Month without mentioning slavery.

Obama, the nation's first black president, says Americans can't understand the Civil War without understanding slavery.

After coming under intense criticism, Virginia Gov. Bob McDonnell apologized on Wednesday and added a paragraph condemning slavery to his Confederate history decree.

Interviewed by ABC News on Thursday in Prague, Obama said the controversy was a reminder to be thoughtful when speaking about “issues like slavery that are so fraught with pain and emotion.''