Topline U.S. open-wheel cars last raced at the Mexico City track in November 2007 when Sebastien Bourdais won the Champ Car season finale.

The venue did not appear on the merged schedule following the Indy Racing League/Champ Car reunification, three months later.

However, sources close to the race's organizers have told Motorsport.com that a deal for IndyCar's return to the city-owned track is now "99 percent done".

The race would be held on August 3-5, as the 14th round of an 18-race Verizon IndyCar Series schedule. For the track, it effectively replaces the World Endurance Championship, which will not be racing in Mexico next year.

On Saturday evening, Hulman & Co. (parent company to IndyCar) CEO Mark Miles confirmed to Motorsport.com that "if the race happens, it's August 5, at least for 2018," and that an alternative date "is really not even in question."

Despite Miles' understandable reticence to consider a new deal done until it's finally signed off, local sources say the reason for the delay in announcing the deal is to avoid detracting attention from this weekend Formula 1 race.

Weather in the Valley of Mexico, where Mexico City is located, is said to be hot in the morning with rain in the late afternoon in August.

One condition of the IndyCar Series racing in Mexico is for at least one Mexican driver to be on the grid. Esteban Gutierrez, who spent three seasons racing in F1, started seven races for Dale Coyne Racing this past season, as substitute for the injured Bourdais.

Coyne has a vacancy in the #19 car since former incumbent Ed Jones was announced as Chip Ganassi Racing's partner for Scott Dixon.

Other vacancies available to Gutierrez would theoretically include AJ Foyt Racing, but team president Larry Foyt says he has not spoken to Gutierrez recently and is "headed in a different direction."

Gutierrez – or any other Mexican driver – could also find a ride with potential new teams Carlin and Harding, while Ed Carpenter Racing has still not confirmed who will race the #20 car on road and street courses.

Additional reporting by Luis Ramirez, Jonathan Noble