by Ralph Russo, Associated Press

Southern Mississippi accepted an invitation to join the Sun Belt Conference on Friday, dealing another blow to Conference USA, which already had six members announce their departures this week.

Two people familiar with the decision told The Associated Press that Southern Miss had agreed to leave a conference it helped found in 1995 and join the Sun Belt at a date to be determined.

The people spoke on condition of anonymity because the Sun Belt was not yet prepared to make an announcement and was still working on more expansion moves that it did not want to address publicly.

Sun Belt Commissioner Keith Gill did not immediately return a message left by The AP.

Yahoo! Sports first reported Southern Miss had agreed to join the Sun Belt.

The Southern Miss news comes a day after the American Athletic Conference announced the additions of six C-USA schools — UAB, Charlotte, Rice, Florida Atlantic, North Texas and UTSA — also at a date to be determined.

Conference USA is down to seven schools committed to the league long-term — Western Kentucky, Middle Tennessee, Old Dominion, Florida International, Marshall, Louisiana Tech and UTEP — and that could be dwindling as the Sun Belt continues to grow.

Various media outlets have reported the Sun Belt has interest in adding Marshall and Old Dominion, and has also discussed inviting FCS powerhouse James Madison.

The chairman of Marshall’s board of governors said in a tweet the university’s decision on conference affiliation will come after a new school president is in place next week.

“The Marshall Board of Governors will name a new president at next Thursday’s board meeting,” Patrick Farrell posted on Twitter. “We’re going to wait until the new president has a chance to provide input before making a decision about our athletics conference affiliation. We’re confident we are in a great position.”

C-USA Commissioner Judy MacLeod released a statement Friday that did not mention Southern Miss’ departure, but said the conference had a “strong core to build around.”

“There are several institutions interested in joining Conference USA, both across FBS and FCS, some of whom we’ve already met with in person,” MacLeod said. “Every step we take will be deliberate, strategically sound, and intentional. We will take the necessary time to add future members that will be the best fit from an athletic and academic standpoint and allow prospective institutions time to complete their process. We continue to believe in the regional concept and will look to incorporate that into our structure and scheduling. There are certainly many questions out there, but a great deal is happening behind the scenes. When appropriate, we will release more information, though out of respect for those involved, we will continue to operate outside of the public space.”

Earlier this month, MacLeod sent a letter to AAC Commissioner Mike Aresco proposing a merger of sorts between the two far-flung conferences. The AAC had no interest and instead poached nearly half of C-USA.

Southern Miss, located in Hattiesburg, Mississippi, fits perfectly in the Sun Belt’s smaller footprint, between Alabama-based schools Troy and South Alabama to the east and Louisiana-Monroe and Louisiana-Lafayette to the west.

USM’s football has a history of success that dates back decades, including Brett Favre leading the Golden Eagles to upsets of Florida State, Alabama and Auburn during his career from 1987-90. Southern Miss won four C-USA titles early in the conference’s existence.

As the composition of C-USA changed, Southern Miss lost many of its longtime rivals such as Louisville, Memphis, Houston and Tulane, and the program has slipped in relevance.

The Sun Belt offers a chance for Southern Miss to decrease travel costs and build new regional rivalries.