* Brazil Bovespa loses 1.21 pct, Mexico IPC down 0.67 pct

MEXICO CITY, Nov 7 (Reuters) - Brazilian stocks plunged on Thursday, falling to their lowest level in nearly a month, on concerns about the future of the U.S. Federal Reserve Bank monetary stimulus program.

Brazil's benchmark Bovespa stock index closed the day down 1.21 percent, while Mexico's IPC index was down 0.67 percent.

Investors in Brazilian stocks took little cheer from news that U.S. economic growth accelerated in the third quarter, with gross domestic product growing at a 2.8 percent annual rate, its quickest pace in a year.

The positive economic data raised questions about the timing of the Fed's tapering of its $85 billion a month bond-buying program, which has helped maintain interest in riskier, emerging market assets that are widely seen to offer better yields.

The preferred shares of the world's top iron-ore miner, Vale SA, which began the day in the black, lost 3.25 percent, despite having reported on Wednesday that third-quarter net income more than doubled from a year earlier.

The company confirmed on Thursday that it is in talks with Glencore Xstrata about potential cooperation between their respective nickel operations in Canada's Sudbury basin in an effort to cut costs as prices languish.

Oil producer Petrobras also suffered, with its shares falling 2.01 percent.

The shares of Eletropaulo Metropolitana Eletricidade de São Paulo SA, Brazil's largest power distributor, jumped 9.2 percent after the company reported a better-than-expected quarterly profit late on Wednesday.

Telefonica Brasil SA shares slipped 3.05 percent after the company posted a 17 percent drop in quarterly earnings on Thursday, partly due to heavy spending on its struggling pay-TV business.

Mexico's IPC index fell 0.67 percent to 40,009.90, thanks to a 0.78 percent decline in shares of telecommunications company America Movil.

Chile's IPSA index was flat at 3,904.28.