By Carla Mozee

LOS ANGELES (MarketWatch) --Brazilian shares slipped Friday, with pressure on mining giant Companhia Vale do Rio Doce following its plans for a $1.6 billion assets purchase, while Mexican shares broke through losses that followed a report that U.S. economic activity shrank to its lowest levels since the 1980's.

Brazil's Bovespa index fell 0.9% to 39,300.79.

In Sao Paulo, shares of market heavyweight Vale (RIO) fell 1.7% after Rio Tinto (RTP) said late Thursday it would sell to Vale the assets of two potash projects for $850 million and an iron ore mine in Brazil for $750 million in an all-cash deal.

Vale is the world's largest producer of iron ore, a key component for the production of steel.

The company "has appeared to pay a healthy premium, despite Rio Tinto's pressure to de-lever, and we note Vale's debt will continue to rise given aggressive dividends, capex and (now) acquisitions planned for 2009," wrote metals and mining analysts at Deutsche Bank in a note Friday.

The broker maintained its hold rating on Vale and its price target of $12 for the miner's U.S.-listed shares. Vale's New York Stock Exchange-listed shares closed down 2.2% at $14.11.

Shares of other steel makers closed lower. Gerdau (GGB) lost 1.1%, Usiminas fell 1.2% and CSN (SID) declined 2.6%.

Shares of Brazil's other market heavyweight, Petroleo Brasileiro (PBR) picked up 1.2% as crude-oil prices edged up 0.6% to $41.48. Oil futures benefited after the U.S. government said economic activity in the fourth quarter contracted less than had been expected by analysts.

Fourth-quarter gross domestic product shrank at an annualized rate of 3.8%, the worst quarterly decline since 1982. Economists had expected a decline of 5.5%.

But the GDP figure would have been worse if the government hadn't counted an unwanted buildup of goods on store shelves as growth, said the Commerce Department. Excluding the inventory buildup adjusted GDP contracted 5.1%.

Mexican equities had started out the session in the red following the gloomy economic report from its biggest trading partner, but they were able to fight their way out of negative territory and pull the IPC index up 0.1% to 19,565.14.

Shares in the manufacturing, home building, consumer products and airline sectors all posted gains.

Steel maker Grupo Simec paced overall advancers with a rise of 6.3%, while decliners are led by engineering firm Ideal.

Cemex (CX) shares finished down 1.3% after the cement maker late Thursday posted a fourth-quarter net loss of $707 million on a 23% sales decline to $4.5 billion. Analysts polled by Dow Jones Newswires had expected a net loss of $242 million.

The company also cut is 2009 capital expenditure plan to about $650 million, a move that the company expects will allow it to save $700 million, up from a previous estimate for cost savings of $500 million.

Shares of America Movil (AMX), the most heavily weighted on the IPC, finished up 0.9%. The wireless services provider's latest quarterly results are due for release Feb. 5.

Chile's IPSA index lost 0.6% to 2,549.46 on Friday and Argentina's Merval lost 1% to 1,074.82.

For the week, the Bovespa rose 3.1%. It posted a 4.7% gain for January, its second consecutive monthly advance.

The IPC finished 1.1% higher for the week. However, the index stumbled 12.6% in January, its biggest monthly loss since October. The monthly decline also marked the worst yearly start for the IPC since 1998, when the index also lost 12.6% in January.

The Merval ended the week with a gain of 1%, and finished 0.2% for January.

The IPSA logged a weekly gain of 2.2%, but outpaced its regional rivals for the month by jumping 7.3%.

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