ATLANTA — Gwinnett County is expected to vote today on a plan to build a new minor-league baseball stadium, which would clear the way for the Braves to move their Triple-A team from Richmond, Va., to the booming Atlanta suburb.

The R-Braves would be Gwinnett’s third professional sports franchise. The county northeast of Atlanta already has arena football and minor-league hockey.

The agenda for the Gwinnett Board of Commissioners included a vote on the purchase of a 12-acre site for $5 million. Commission chairman Charles Bannister did not immediately respond to a telephone message left at his office.

The Braves said they would have no comment on the proposed move until after the county vote, which was expected to be a mere formality.

A person familiar with the talks, speaking on condition of anonymity because no official announcement had been made, said there already were plans for a news conference this afternoon at The Arena at Gwinnett Center.

The proposal calls for one lame-duck season in Richmond before the International League team moved to suburban Atlanta in 2009.

The Braves have been in talks with Richmond officials over building a new stadium to replace The Diamond, a 12,134-seat facility that opened in 1985 and was considered economically inferior to newer Triple-A stadiums.

The contract to play at The Diamond runs through the 2010 season, but there is an option to pull out each year if notice is given by Oct. 1.

In response to media inquiries, the city of Richmond released e-mails showing its chief financial officer, Harry Black, was still in talks with Mike Plant, the Braves’ executive vice president, over possible sites for a new stadium in the past two weeks.

Linwood Norman, a spokesman for Richmond Mayor L. Douglas Wilder, had no comment other than, "We’re waiting to hear."

Richmond has been home of the Braves’ top minor-league affiliate since the team moved from Milwaukee to Atlanta in 1966.

Gwinnett, a sprawling county with a population estimated at more than 750,000, already has two pro teams at its 11,500-seat arena, which opened in February 2003.

The Georgia Force of the Arena Football League are moving back to the suburbs this season after playing at Philips Arena in downtown Atlanta. The Gwinnett Gladiators are an ECHL hockey team affiliated with the NHL’s Atlanta Thrashers.

A new stadium would cost much less than the $90 million arena, which was funded through a combination of development bonds and hotel-motel taxes.

Last summer, the county released a feasibility study that showed Gwinnett could support a baseball team, and the least one independent league talked openly about wanting to put several teams in the greater Atlanta market.

The Braves were surely eager to pre-empt such a move by bringing in a team of their own, though having a minor league affiliate less than an hour’s drive away from Turner Field could cut into the big league club’s fan base.

However, the Braves were likely encouraged by teams that have thrived in the suburban shadow of big league clubs, such as the Double-A Frisco RoughRiders (near Dallas) and the Class A Lake County Captains (suburban Cleveland) and Kane County Cougars (west of Chicago).

The Seattle Mariners have their Triple-A team in Tacoma, a major city in its own right but only about 30 miles from Safeco Field.