A key deadline arrived Wednesday in the effort to keep the NFL in St. Louis.

The St. Louis Convention & Visitors Commission was due to give the St. Louis Rams its plan to upgrade the Edward Jones Dome, a key step in whether the franchise stays put.

Details about the plan have not been released. Donna Andrews, a spokeswoman for the CVC, declined comment. Officials with the city of St. Louis and St. Louis County also declined comment. Team spokesman Artis Twyman said the proposal was expected to arrive later in the day.

The Rams will have until March 1 to accept or reject the offer. They can also make a counterproposal. Arbitration would begin June 15 if no agreement is reached, and the arbitration process could last through the end of the year.

Public money built the dome, which opened in 1995, the year the Rams relocated to St. Louis from Los Angeles. It was financed largely with $256 million in revenue bonds, a debt that is being paid back with $24 million annually in tax money — $12 million from the state of Missouri and $6 million each from St. Louis city and county.

The St. Louis Post-Dispatch reported that the Rams pay $500,000 each year to use the dome — $250,000 in rent and $250,000 for reimbursement to CVC for game-day expenses. The team gets to keep box office receipts, most advertising revenue, net game-day concession proceeds, and some concession proceeds sold for non-football events. The lease also allows use of Rams Park, the practice facility in St. Louis County.

But the 30-year lease that runs through 2025 also requires that the dome remain among the "top tier," or top eight, of the 32 NFL teams measured by various criteria. Critics contend it would be virtually impossible to bring the 17-year-old stadium to that level, especially since only 10 NFL stadiums are older than the dome and some of those have undergone multimillion-dollar renovations.

The agreement between the CVC and the Rams allows the lease to be broken every 10 years if the dome falls short of "first tier." About $30 million in publicly funded improvements persuaded the Rams to maintain the lease after the 2005 marker, and now another deadline has arrived in which the Rams could break the lease after the 2014 season if the dome isn't in the top tier.

Owner Stan Kroenke figures to be seeking a more significant upgrade this time.

Kroenke has been non-committal about the future of the team, which has fans worried. Kroenke, who is married to the daughter of Wal-Mart co-founder James "Bud" Walton, is a native Missourian, but he also owns an estate in Malibu, Calif., and is among the finalists seeking to buy baseball's Los Angeles Dodgers, leading to speculation about a possible move to California.

Or London. Those concerns were raised last month with the announcement that the Rams will play one "home" game each of the next three seasons in London, where Kroenke owns a majority share of the English soccer club Arsenal. NFL Commissioner Roger Goodell has often spoken of possibly locating a team in London. The CVC contends the games in England violate a lease agreement requiring all home games to be played in the dome.

Kroenke's only recent public appearance in St. Louis came last month when he introduced Jeff Fisher as the new coach of the team that was 2-14 last season and an NFL-worst 15-65 over the past five seasons. Asked about the future of the Rams in St. Louis, Kroenke passed on the opportunity to assure fans he had no intention of moving.

"The chronology of what occurs with the lease is public knowledge," he said. "I don't think for me to comment on that process is ... particularly timely."

Kroenke did note that he has a long history with the Rams in St. Louis. He purchased a 40 percent share of the team when Georgia Frontiere moved the Rams here. She died in 2008, and two years later, Kroenke bought the remaining stake from her children.

St. Louis has lost an NFL team before, and a stadium issue was at the heart of that move. Bill Bidwill moved the Cardinals to Arizona following the 1987 season after years of failed attempts to get a football-only stadium. The football Cardinals shared old Busch Stadium with the baseball Cardinals.