IndyCar chairman Mark Miles said it is “unlikely” that the series will open its 2016 schedule in Mexico City, delaying for at least a year a February launch that would have extended the season over eight months.

Miles told USA TODAY Sports that he expects the finalized 2016 schedule to feature 16 races on 15 dates — the same as this past season after the planned opener in Brasilia, Brazil was canceled — and extend by a few weeks into mid-September. The street course race in Detroit featured a doubleheader last season.

While the exploration of international venues has often been unpopular with owners seeking to contain costs, an expansion of the schedule had been eagerly anticipated to maximize investments in personnel and equipment. Miles’ desire to avoid direct competition with the NFL and NASCAR‘s Chase for the Sprint Cup in the fall made an earlier debut more attractive and would have shortened what is now a seven-month off-season.

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The final “highly, highly likely” piece of the schedule, he said, depends on board approval from another venue on or around Oct. 13. That venue, he said, is not Pocono Raceway.

“While the management is for it, the board is the board, so they actually make these decisions,” Miles said. “So while I don’t want to count the chicken completely before it’s hatched, I think that is really the remaining thing.

“If we had to, we probably could put this out, in theory, sooner, but we want to go through the formality and respect the process of a formal approval from one of the promoters.”

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Gateway Motorsports Park owner Curtis Francois reportedly is interested in adding IndyCar to a slate of NHRA and NASCAR events at the venue outside of St. Louis.

Miles said concerns over proper promotion for the Mexico City race, IndyCar’s first junket outside of the United States or Canada since Sao Paolo, Brazil in 2013 – prompted the series to refocus on 2017.

“The process they needed to go through to get everything lined up has not really left a lot of time to be confident that everything can be done to properly promote the first race,” he said. “So I think the conversation is very much about ‘17. We just kind of ran out of time for ‘16.”

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The Grand Prix of St. Petersburg will again therefore serve as the season-opener on its revised, earlier March 13 date.

Miles called a proposed April 2 visit to Phoenix International Speedway “highly likely” and said he was “very optimistic” about a return to Pocono, where attendance has disappointed track officials. Track president Brandon Igdalsky told the Associated Press that he wants “five big events in five months and IndyCar is in that plan,” but has yet to announce a decision.

Driver Justin Wilson died on Aug. 24 as a result of a traumatic head injury sustained during the Pocono race the previous day. Wilson was struck by a piece of debris that soared high above the racing surface after a crash by Sage Karam. Miles said the series would like Pocono to heighten some of its retaining fencing before a return.

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Officially announced earlier, Road America will return to the open wheel schedule on June 26, with a Boston street race scheduled for Sept. 4. Sonoma Raceway is likely to move from its late August slot to mid-September to complete the schedule.