Texas A&M is set to join the Southeastern Conference, the league said Sunday, possibly signaling legal hurdles have been cleared for the Aggies to leave the Big 12.

The SEC announced the move will be effective next July, and said Texas A&M will participate in all sports during the 2012-13 academic year. That gives the SEC 13 members and its first addition since South Carolina and Arkansas joined in 1992.

The Aggies' defection from the Big 12 had been held up by the possibility of legal action from Baylor and other members, but sources told ESPN's Joe Schad that the school's play in the conference next year is "unconditional." If any school, including Baylor, files litigation against A&M, it would be addressed at that time.

A Big 12 administrator said neither the SEC nor Texas A&M have asked any of the Big 12 schools to waive their right to sue. The person spoke Sunday night on condition of anonymity because of the sensitivity of the situation.

A&M's rights change in course was due, a source told ESPN.com's Andy Katz, to the sense the Big 12 will now stay together following the Pac 12's decision not to expand. The source said there is now no longer any fear that the remaining schools will claim they were financially damaged by the Aggies' departure.

SEC presidents and chancellors voted in favor of the move on Sept. 6, and a source said A&M's negotiation of an exit fee with the Big 12 "will now begin in earnest."

"We are excited to begin competition in the nation's premier athletic conference," Texas A&M President R. Bowen Loftin said in the statement.

It's unclear if the SEC will add a 14th member for next season or go with unbalanced divisions. Rumored possibilities include the Big 12's Missouri and West Virginia of the Big East.

Texas A&M began the courtship in July, unhappy with rival Texas' Longhorn Network -- a 20-year, $300 million venture

with ESPN -- and stirred another turbulent period for the Big 12.

The Aggies, who play Arkansas on Saturday, give the SEC entry into major TV markets such as Houston and Dallas.

"Texas A&M is a nationally prominent institution on and off the field and a great fit for the SEC tradition of excellence -- athletically, academically and culturally," Commissioner Mike Slive said in the statement.

Slive, Loftin and others will hold a news conference Monday evening in College Station, Texas.

Four Big 12 teams -- Oklahoma, Texas, Texas Tech and Oklahoma State -- had explored moving to the Pac-12, which decided not to expand this year.

Oklahoma President David Boren said the nine remaining schools besides Texas A&M agreed last week to give a six-year grant of their first- and second-tier television rights to the Big 12. That means all revenue from the top television games -- shown currently on networks owned by ABC/ESPN and Fox -- would continue to go to the Big 12 even if a school bolts to another league.

That deal, however, had not been finalized.

The Big 12 also ousted Commissioner Dan Beebe last week after five years and replaced him with former Big Eight Commissioner Chuck Neinas on an interim basis.

"I am personally saddened to see Texas A&M depart from the Big 12, and wish I had the opportunity to visit the campus to sit down and talk with their administration," Neinas said in a release. "We will continue to work diligently in securing the long-term stability of the Big 12.

"Now that the status of Texas A&M has officially been determined, the membership can focus on the desired course for the Conference moving forward. Although no timeline has been established, an expeditious pursuit is anticipated."

A&M's official departure from the Big 12 was considered the next step needed to determine where this round of conference realignment is headed.

Once that is done, the SEC can decide on a 14th member, if it wants one and the Big 12 can replace the Aggies.

Texas A&M moved to the Big 12 after 82 years in the Southwest Conference and its departure to the SEC will mark the first time the Aggies won't be in a conference with rival Texas and Baylor.

Some are worried A&M's departure will jeopardize the future of the annual football game, currently played on Thanksgiving night, between the Aggies and Texas.

"There is some lamenting about (losing) some of the good competition we've had over the years with everyone (in the Big 12)," Texas A&M faculty athletic representative Tom Adair said. "Of course, Texas is the big one. I hope it will be worked out and we will continue."

It is one of the oldest rivalries in college football, with the teams first meeting in 1894.

Loftin said he'd like to continue the rivalry no matter what conference the Aggies were in when he announced the school's plans to explore its conference options in August.

However, even if the schools were able to work out a deal to meet for a nonconference football game each season, it would be nearly impossible to guarantee that other sports such as men's and women's basketball and baseball would be able to meet their biggest rivals each season.

Information from ESPN.com senior writers Andy Katz and Pat Forde, ESPN college football reporter Joe Schad and The Associated Press was used in this report.