UPDATE: The Big 12 has extended an invite to TCU and TCU is expected to accept the invite, according to CBSSports. Here is a link to the breaking news story.

TCU would have to pay a $5 million dollar exit fee to the Big East, but would not have to wait 27-months to join the conference, like Pittsburg and Syracuse might to join the ACC.

After Missouri authorized its chancellor to explore other conference affiliations, the Big 12 has stepped up its efforts for expansion, according to reports.

The most likely options for the Big 12, which would drop to eight members if Missouri left for the SEC, are BYU, Louisville, TCU, and West Virginia, according to OrangeBlood's Chip Brown.

BYU has long been rumored to be an object of the Big 12's affection -- the Upset reported last week that BYU already has an offer from the conference -- but there are some questions whether the school would be willing to give up its recently obtained football independent status to join the shaky conference.

BYU also has its own television channel, BYUTV, which is very similar to Texas' Longhorn Network. The Longhorn Network, which planned to show conference and high school football games, angered Texas A&M so much it left for the SEC and almost caused Oklahoma to bail for the Pac-12.

BYU's network hasn't had near the mpact that the Longhorn Network already has, especially because of the fertile Texas recruiting grounds, but it still could anger a few of the Big 12 conference members.

The remaining viable candidates all reside in the hanging by its last thread Big East conference. TCU actually doesn't officially join until 2012 -- making it an easier grab for Big 12 because it wouldn't have to wait 27 months if the move is completed by June 30th 2012.

TCU is a football program on the rise with coach Gary Patterson and would help secure more of that lucrative Texas market, though some have speculated Texas might not be completely okay with another Texas school joining the conference. One of the reasons is Texas might not want to give up any leverage in Texas recruiting circles, which allowing a TCU or a SMU into the conference might do.

Louisville and West Virginia represent the best of the rest in the Big East for football and geographic reasons for the Big 12. Louisville's struggled a bit in recent years in football, but showed under now-Arkansas coach Bobby Petrino that the program could flourish with the right coach. The money is there and while not the perfect geographic fit that TCU is, Louisville could fit in well with the rest of the Big 12.

Louisville basketball coach Rick Pitino railed against other schools, notably Connecticut, leaving the Big East in a recent interview with Adam Zagoria. But Syracuse basketball coach Jim Boeheim was opposed to the school's move to the ACC and that clearly didn't stop them, so it's doubtful that Pitino alone would stop Louisville from moving to the Big 12.

West Virginia has privately expressed interest in joining the ACC and SEC only to be rebuffed, according to many media reports. The Mountaineers aren't known for particularly stellar academics, but boast a strong football program and passionate fan base.

The Big 12 has assembled a five person expansion committee and will review possible candidates for admission. How quickly they move on expansion is anyone's guess, but the conference figures to move aggressively while still keeping an eye on what Missouri decides to do.