The original 2030 bid was by Argentina and Uruguay, with neighbours Paraguay and Chile joining later.
"Today I think we are favourites to win," Alejandro Dominguez told reporters. "If we do our job at Conmebol and the countries do theirs then we are favourites to win."
Dominguez was speaking after a meeting with the presidents of the four bidding nations at the UN Conference on South-South Cooperation in Buenos Aires.
Bid coordinator Fernando Marin told Reuters there was no chance of adding a fifth country to the mix.
"The incorporation of Chile and with CONMEBOL involved reinforces the Southern Cone's aspirations," Marin said, adding that the four countries will meet on April 8 in Buenos Aires to discuss the bid.
The multi-nation bid is designed to coincide with the 100th anniversary of the first World Cup which took place in Uruguay in 1930.
The four South American nations are expected to face stiff competition, with Morocco, Spain, Portugal and England among countries to express interest in hosting the event.
The 2022 World Cup will be held in Qatar and the 2026 tournament in the U.S., Mexico and Canada.
(Reporting by Ramiro Scandaolo, Writing by Andrew Downie, editing by Ed Osmond)
