Texas A&M’s departure from the Big 12 Conference drew closer to reality on Monday when the university’s president, R. Bowen Loftin, called the Big 12 board chairman, the Missouri chancellor Brady Deaton, notifying the league that the Aggies would formally withdraw — very likely on Tuesday — according to two college officials with direct knowledge of the decision.

This latest step in the Aggies’ effort to join the Southeastern Conference appears to have two stumbling blocks. The first is Texas A&M’s exit fee from the Big 12, which it has not negotiated. That amount is expected to be close to $15 million. The other is the approval of the S.E.C. presidents. Nine of the 12 would have to vote in favor for Texas A&M to become a member of the conference. It is unlikely that Texas A&M would be this far along in the process without adequate S.E.C. presidential support.

Texas A&M hopes to play in the S.E.C. during the 2012 football season, which would appear to leave the conference with a mathematically clunky 13 teams for one year.