Two groups of California tribes announced Tuesday that they will oppose ballot initiatives that seek to overturn deals that allow four American Indian tribes, including the Pechanga Band of Mission Indians near Temecula, to get more slot machines.

The ballot initiative, which was created by a workers' union and a racetrack owner from San Mateo, is also supported by the Pala Band of Mission Indians near Fallbrook. Pala, which competes with Pechanga and says that the Temecula tribe's deal with the state is unfair, contributed $500,000 to the initiative campaign.

The groups that announced their opposition to the initiative Tuesday are the Tribal Alliance of Sovereign Nations in San Jacinto and the California Nations Indian Gaming Association in Sacramento. The alliance represents 14 tribes, including Pechanga. The association represents 65 tribes.

Both called the ballot initiative an attack on the sovereign right of tribes to negotiate gaming deals with the government.

Initiative supporters say the deals would create megacasinos that have an unfair advantage. They need to collect 434,000 signatures by Oct. 8 to put the matter before voters in February.