Anheuser-Busch InBev, the world's largest brewer, said it faced a challenging start to 2010 with U.S. consumers drinking less after it unveiled mixed fourth-quarter earnings buoyed by a sharp rise in Brazil sales.

The maker of Budweiser, Stella Artois and Becks said on Thursday it expected to sell slightly more beer this year than last, but profit growth would be only a single-digit percentage in the first quarter before increasing through 2010.

In the first three months in particular it would face tough comparisons with a strong U.S. performance last year, exacerbated by bad weather early in 2010, and lower Russian sales because of fourth-quarter stocking ahead of a tax hike.

Sales, marketing and administrative expenses would be higher year-on-year in the first half.

We see no improvement in the operating environment today, Chief Financial Officer Felipe Dutra told a conference call, adding that the company was stronger now that the distraction of its post-merger divestment program was behind it.

For the full year we expect beer volumes to be in positive territory, he said.

AB InBev shares slid as much as 4.2 percent to 36.25 euros in early trading, but by 1238 GMT were down 1.6 percent.

They are barely changed in the year to date compared with a 4 percent rise in the Eurostoxx food and beverage index, which was virtually flat on Thursday.

Analysts said the weakness was due to lower-than-expected fourth-quarter core profit (EBITDA) and a muted outlook, with debt reduction and savings already priced into shares trading at a premium to rivals Heineken and SABMiller.

I think they are being appropriately cautious with their outlook, said Trevor Stirling, analyst at Bernstein Research.

STRONG BRAZIL, U.S. SLIPPAGE

The company said it sold some 2 percent less beer in the fourth quarter in the United States, where it has about half of the market, but achieved higher prices and cut costs.

Strong sales in key market Brazil, where AB InBev pushed its market share to 70 percent, and the strength of that country's real currency were behind a 5.1 percent hike in group sales, more than the market had expected.

The company's much-watched EBITDA core profit rose an underlying 11.5 percent to $3.11 billion in the fourth quarter, against the $3.27 billion average forecast in a Reuters poll of 15 analysts.

AB InBev said it achieved $235 million of savings in the fourth quarter from the 2008 merger of Belgium's InBev and U.S. Anheuser-Busch, bringing the full-year total to $1.11 billion.

The company had a 2009 savings target of $1.0 billion and $2.25 billion by 2011. It kept this forecast, although some analysts had expected the brewer to set its sights higher.

Recession-hit consumers in mature, developed-world markets bought less beer last year but stomached higher prices. Brewers with greater emerging-market exposure registered gains and all focused on squeezing out savings.

AB InBev, with a 50:50 developed to emerging market split, sold 0.7 percent fewer drinks last year, but 1.0 percent more in the fourth quarter.

Chief Executive Carlos Brito said western Europe was set to decline longer-term, but was more upbeat on the United States, the world's most profitable beer market.

We're very bullish in the U.S... but recognize that until the economy gets better we're going to have tough years, he said.

Heineken, with some 70 percent of its profits from Europe and North America, reported a 6.7 percent drop in volumes in the fourth quarter, but Carlsberg's volumes stayed unchanged after declining in the first nine months..

Underlying beer volumes were also flat for SABMiller, the world's No.2 brewer.

InBev bought rival Anheuser-Busch for $52 billion, raising $9.8 billion from a rights issue late in 2008 and $9.4 billion from divestments during 2009, bringing net debt to EBITDA down to 3.7 times from 4.7 at the end of 2008.

(Reporting by Philip Blenkinsop; editing by Dale Hudson, Mike Nesbit)