The former Sunderland and Ipswich Town manager has insisted that he will put Ireland first if he feels that he is unable to combine both roles.
"I feel that if I am taking my eye off the ball with Ireland, then I will leave Aston Villa," Keane told Sky Sports News. "There is no doubt about that. I have told Paul Lambert that, told Martin that and told the FAI that.
"I didn't just jump into it with Villa. I sat down with Paul Lambert, had a think, and sat down Martin and the FAI and thought, I can adapt to this.
"It felt like a full-time job, but, having been in the Ireland job a while, I felt I could manage to do both."
Ireland face Germany in a Euro 2016 qualifier this evening.