The Big 12's presidents have decided to allow their conference to proceed toward playing the 2020 college football season this fall despite the Big Ten and Pac-12 canceling their 2020 seasons on Tuesday, multiple conference sources told CBS Sports on Tuesday night. League sources said earlier that the Big 12 was leaning in that direction prior to an evening conference call.

The Big 12 will announce its schedule -- consisting of nine conference games and one nonconference showdown -- by Wednesday morning with a start date of Sept. 26, the traditional Week 4, conference sources told CBS Sports. The SEC is also starting on that date, while the ACC aims to begin the week of Sept. 7.

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On the Tuesday night call, Big 12 presidents heard from medical experts before going into executive session discuss new information they learned about COVID-19 and the ongoing pandemic. The Big 12 presidents were expected to be joined by league athletic directors for another conference call by the end of the evening, all on the topic of the viability of playing college football this fall.

"The mindset is it's too early [to cancel]," a Big 12 source told CBS Sports before the meetings. "Unless the medical folks flip the switch, [we'll go]."

Coming out of the calls, the Big 12 is expected to enhance its coronavirus testing as part of its adjusted procedures. Among those enhancements will be cardiac testing for COVID-19 positives, according to Yahoo Sports' Pete Thamel.

Big 12 commissioner Bob Bowlsby has been supportive of playing almost from the beginning of the discussion. He has repeatedly warned that there will be a "disruption" in the season.

"If there is," the source said, "we'll pull the plug."

The means the Big Ten and Pac-12 decisions won't necessarily cause the shutdown tsunami that was speculated.

CBS Sports reported Monday the ACC "absolutely" is proceeding as if football will be played in the fall. A Duke doctor on the ACC medical advisory board took to Twitter on Tuesday saying football could be played in the fall.

SEC commissioner Greg Sankey continues to make the media rounds saying his conference will take a deliberate approach with their medical experts giving the league a green light to play. There is little doubt which way the SEC is leaning.

That leads to a possible split with the Big Ten and Pac-12 attempting to play in the spring while the other three Power Five leagues give it a go this fall. The Big 12 may be somewhat of a linchpin to the ACC and SEC playing as a potential swing decision that could affect the majority one way or another