The Pumas are reportedly close to joining the tournament alongside Australia, New Zealand and South Africa.
But Contepomi, 29, told www.aplenorugby.com.ar: "It would be complete madness because the structure of our rugby is not prepared for that.
"We would have to make a change in both our domestic tournament and the Union.
"Also, most of the national team players are in Europe and have responsibilities with our clubs. Tri-Nations is played while the most of us are on holidays and we have to rest.
"In this kind of sport, with physical contact, this is crucial.
"We cannot play with the national team without resting after a season, because it would affect our clubs and they would not allow us to play."
Contepomi, who plays club rugby for Leinster in Ireland, wants to see the Pumas entered into the RBS 6 Nations championship.
The annual tournament is contested by European nations England, Ireland, Scotland, Wales, France and Italy.
He said: "I'd prefer to play in the Six Nations, because it would be a very good championship for all of us and we would be fighting for something important.
"The Six Nations has a very important history and each game is different.
"It is not the same, but if we consider the Test matches we recently played against those teams, at home and abroad, we demonstrated we can beat everybody."