COLLEGE STATION, Texas -- Southeastern Conference commissioner Mike Slive welcomed Texas A&M as the 13th member of the league on Monday and said he doesn't expect to add another team before the Aggies begin play next season.

The SEC announced Sunday that Texas A&M would leave the Big 12 to join the conference next July and will compete in all sports for the 2012-13 academic year. The Aggies are the first newcomers since South Carolina and Arkansas joined the conference in 1992.

In an event complete with Texas A&M's band, yell leaders, collie mascot Reveille and hundreds of fans, the Aggies ushered in a new era with a pep rally-type celebration of the move.

Slive and Florida president Bernie Machen, chairman of the SEC leaders, took turns on a stage decorated with maroon and white balloons and adorned with A&M's national championship trophies from various sports as well as an SEC logo that included the Aggies.

Texas A&M president R. Bowen Loftin and Texas A&M athletic director Bill Byrne addressed the crowd and raved about their excitement in joining the SEC.

Slive said the SEC wasn't looking to expand, but that A&M was too attractive of an option to ignore.

"We were very happy at 12," Slive said. "When Texas A&M came to us and indicated their interest in joining the SEC, we said to ourselves: 'That is a great institution, academically, athletically, culturally and in every way, and a real fit.' So we decided even though we were content with 12, that we had the opportunity to have Texas A&M as part of the SEC was something that we just did not want to give up."

Slive acknowledged that scheduling a 13-team league will be difficult but said it wouldn't expand just to make things easier.

SEC presidents and chancellors voted unanimously for the move on Sept. 6, but the official announcement was delayed because of the possibility of legal action from Baylor and other members.

Sources told ESPN's Joe Schad on Monday that the school's participation in the conference next year is "unconditional." If any school, including Baylor, files litigation against A&M, it would be addressed at that time.

Slive said this fear was quelled when Oklahoma decided it would stay in the Big 12 and keep the remaining nine teams together. The SEC was given no assurances that schools would not take legal action, but decided Oklahoma's decision was enough to go ahead with A&M's admission into the conference.

Oklahoma, Oklahoma State, Texas and Texas Tech looked into defecting to the Pac-12, but the league decided not to expand this year.

That left the remaining schools in the Big 12 in need of a plan to save the conference. The nine remaining schools 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, according to Oklahoma President David Boren.