Gerardo Martino says he has not done anything differently to get Lionel Messi to replicate his Barcelona form for Argentina.

Messi has been the standout player of the Copa America Centenario so far, ahead of Sunday's final against Chile at the MetLife Stadium in East Rutherford, New Jersey.

The 29-year-old has scored five times, surpassing Gabriel Batistuta as his country's all-time leading scorer in the process, and many back in Argentina are saying he is finally putting in the type of performances that have, until now, only been seen with Barca.

Martino, however, believes Messi has been at the top of his game for some time, and says it is all down to the atmosphere in the camp.

"In reality I think that for a long time now he’s been performing very well with the national team," he said during a news conference. "He’s had many more positive performances than not so good performances and I certainly don’t think anything is different from the people working around him now.

"He’s found the same form as at Barcelona. He’s playing with the same people for a long time now, he’s happy, he’s in a good place, as he was in Brazil, and he’s still happy now."

Martino also confirmed that Angel Di Maria, Javier Pastore and Nico Gaitan will be available for selection when he comes to name his starting XI against Chile on Sunday, although Augusto Fernandez and Ezequiel Lavezzi are both ruled out.

But the Argentina coach cautioned that his men will not only be up against the side that beat them in last year's Copa America final but one of the world's top teams.

"Chile for me is one of the best national teams in the world," he said. "It’s not their growth compared to us but how we’ve grown compared to Chile. I think that’s a good comparison.

"Chile develop their game and apply pressure — to me, they are their main weapons and makes them one of the best teams in the world."