Defender Clark, who played 78 minutes of last Saturday's goalless draw with Chelsea, was born in London and has captained England Under-18s.
But he has decided to commit to playing at senior level for Giovanni Trapattoni's side as an act of faith for the backing he received from his Irish-born mum and dad.
Clark said: "Why have I chosen to play for Ireland? For myself and my family.
"My family have done a lot for me over the years, since I was a little boy. I owe them a lot so I've made this decision for them.
"Richard Dunne (Villa and Ireland defender) mentioned it to Ireland and they looked into it and got in contact with me and the club. They gave me time to think about it and about my decision.
"If all the paperwork has gone through by the next game, I'll be in contention so fingers crossed that happens."
Clark, regarded as one of Villa's brightest prospects, added: "I was England Under-18 captain but I didn't think I was going anywhere really with that.
"When a young lad gets an opportunity like this, it is hard to turn down."