The Australian fast bowler will play a leading role for Brisbane Heat on Saturday as they seek a win against the Adelaide Strikers to keep their Big Bash League title defence alive.
But Harris said he won't nominate for the IPL, in a bid to extend his international career into next year, at the behest of Australian coach Darren Lehmann and national high performance chief Pat Howard.
"There is a lot of money involved (in the IPL) and with me coming towards the end of my career, you have got to try to maximise your career earnings," Harris told reporters in Adelaide on Friday.
"But when Darren and Pat Howard came to me and said `we want you there in 2015' - that made the decision for me.
"The fact that they're looking at a 35-year-old, by then; that they still want me involved in their team, that made the decision for me.
"I want to play for Australia as long as I can.
"I'd love to be able to do it all but in reality, my knee is going. So I have to make tough decisions and that is one of them."
Harris said he had been troubled by knee pain for almost two years.
"I have learnt how to manage it ... I can put up with a hell of a lot of pain with it," he said on the eve of the Heat's must-win clash against the Strikers.
Brisbane claimed the BBL title last summer after facing a similar predicament: having to win their last two fixtures just to make the finals.
"Two games left, two wins - it's as simple as that," Harris said.
"If we do that, we sneak into the finals. It's the perfect situation for us, it gets us going."
Adelaide also must win their last two matches to secure a finals berth and have recalled top batsman Michael Klinger from a hamstring strain for the Adelaide Oval fixture.