* Fed's Bernanke dampens bets for more US stimulus
* ECB liquidity offer fails to drive stocks higher
* Brazil Bovespa down 0.22 pct; Mexico IPC down 0.54 pct
By Michael O'Boyle
MEXICO CITY, Feb 29 (Reuters) - Latin American stocks dipped on Wednesday after Federal Reserve Chairman Ben Bernanke undercut hopes the Fed may pump up banks with more liquidity that could support bids for equities.
The MSCI Latin American stock index fell 0.46 percent, slipping off a seven-month high. The index advanced nearly 5 percent in February.
Bernanke, in testimony before U.S. lawmakers, gave a mixed view of the U.S. economy and did nothing to support hopes by market players that more monetary stimulus may be coming.
"Bernanke came out and changed everyone's opinion, and we saw stocks and commodities fall," said Gerardo Roman, head of stock trading at brokerage Actinver in Mexico City.
Still, traders said the Fed's commitment to keep its interest rate near zero in the coming years as well as rock-bottom rates in other parts of the world would shore up demand for riskier assets, such as Latin American stocks.
The region's major stock indexes have struggled to rise above key resistance levels during February as investors waited to see if Europe's debt troubles will wane and if the global economy will pick up.
Buyers have stepped in whenever stocks dipped, but even though Latin American prices rose, volumes waned through the month, underscoring a lack of conviction in further big gains.
"We are on the line here, and the question is weather this could become a bull market or not. There is a lot of money still on the sidelines ready to come in if we break through these levels," Roman said.
Shares rose in early trading after Europe's banks seized on 530 billion euros in cheap three-year loans from a second offering in three months by the European Central Bank.
The liquidity boost could help support demand for riskier assets as banks use cash to buy higher-yielding instruments and speculators mimic the bets.
But the ECB's boost may not pack as big of a punch as the last cash injection did in December when Latin American stocks rallied 21 percent before stalling out around current levels in early February.
"The gains from the ECB auction were expected, so people weren't ready to buy into the idea that those would continue in the short-term," said Ruy Araujo, an analyst with Metodo Investimentos in Sao Paulo.
In Brazil, the Bovespa index hit its highest level since late April before falling back to close down 0.22 percent at 65,811.73. The Bovespa has struggled this month to break past the 66,400 level.
The index finished February with a 4.3-percent gain, helped be expectations that Brazil's central bank will keep cutting its benchmark interest rate, now at 10.5 percent, down to the single digits this year.
Homebuilder Gafisa lost 7 percent after announcing it had rejected an offer from private equity firms GP Investimentos and Equity International to purchase part of the company.
Mexico's IPC index fell 0.54 percent to 37,816.69. The index added 1 percent in February, but it has been unable to hold onto gains past 38,300.
Shares in bottler and convenience store operator Femsa lost 2.19 percent.
America Movil, the telecommunications firm controlled by billionaire Carlos Slim, rose 0.46 percent.
Mexico's stock exchange is raising America Movil's weight to 25 percent of the IPC from just above 22 percent, effective Thursday. Its shares rose about 2.5 percent on Tuesday partly in anticipation of the change, traders said.
Chile's IPSA index rose 0.33 percent higher after manufacturing output there grew a faster-than-expected 3.7 percent in January, driving up industrial conglomerate Copec by 1.65 percent.
The IPSA added 6.5 percent in February.