General Motors Co. do Brasil Ltda. plans to develop two new Chevrolet models at its assembly plant in Gravatai, Brazil.

The vehicles are scheduled to bow in 2012 and will be sold domestically as well as exported to other Mercosur nations. General Motor Co. spokesman Richard James declines to reveal what the new vehicles will be, saying details will be released closer to their introduction.

Production of the new models is made possible by GM’s recently announced $1 billion investment in its Mercosur operations, a project internally codenamed “Onyx,” James says.

Of the total investment, $700 million will be directed toward GM’s Gravatai plant, which will see its annual capacity increase threefold to 360,000 units. The site currently produces the Chevrolet Celta and Prisma, both of which are best-sellers in Brazil and will continue in the market, GM says.

The investment is expected to boost employment at Gravatai and 17 nearby suppliers by 1,000 jobs, the auto maker says.

The remaining $400 million earmarked for Onyx will be invested in other GM Brazil operations.

The Onyx project demonstrates the importance of the Mercosur region to GM, which last week emerged from bankruptcy protection in the U.S.

According to GM data, Brazil is the auto maker’s third-largest market behind the U.S. and China. In 2008, GMB set an all-time yearly sales record with 548,991 deliveries, a 10.1% increase over 2007’s total of 498,758.

In June, GMB sales totaled 58,646 units for a 12.5% jump, compared with like-2008. Through the first half of this year, GMB deliveries were down 5.9%.

The auto maker’s investment represents the second expansion GM has made in Gravatai. The first, in 2006, saw the auto maker spend $240 million to launch the Chevrolet Prisma sedan and to expand capacity to 230,000 units per year.