Generic competition and pricing pressures weighed on AstraZeneca's sales in the third quarter, ahead of a key challenge to its top-selling cholesterol drug Crestor in the U.S. marketplace.

A weaker dollar provided some protection to Britain's second-biggest drugmaker, with sales at the reported level up 4 percent at $8.21 billion (5.12 billion pounds), although in local currencies revenues were down 2 percent.

The result was slightly better than expected. Analysts had, on average, forecast sales of $8.16 billion, according to Thomson Reuters I/B/E/S.

Core pretax profit, which excludes some items, was flat at $3.08 billion, equivalent to core earnings per share up 14 percent at the reported level to $1.71.

The company raised its core EPS target for the full year to between $7.20 and $7.40, from $7.05 to $7.35, largely on currency movements.

AstraZeneca faces a major challenge to Crestor from the end of next month, when generic copies of Pfizer's
market-leading cholesterol fighter Lipitor are due to hit the U.S. market.

Results from a head-to-head study last month failed to show Crestor was better than Lipitor in reducing clogging in coronary arteries, putting the medicine at increased risk from generic Lipitor.

(Reporting by Ben Hirschler)