UPDATE 1-Alibaba.com falls below IPO price ahead of results

(Update with quote and stock prices)

HONG KONG, March 18 (Reuters) - China's top e-commerce firm Alibaba.com (1688.HK) tumbled below its IPO price for the first time on Tuesday ahead of its 2007 earnings report due later in the day.

"Nasdaq-listed Chinese Internet companies were trading sharply lower across the board. Given Alibaba is a high-beta stock and it has direct exposure to the U.S. economic slowdown through growing SMEs and online marketing, that may explain why it is sinking below the IPO price today," said Glenda Yu, analyst at Cazenove.

The stock fell more than 22 percent, or HK$3.44, at one point to an all-time low of HK$12 before finishing the morning at HK$12.98, still below its IPO price of HK$13.50 and down about 16 percent from the previous close.

A total of 11.98 million shares worth HK$161.4 million changed hands.

Alibaba.com, whose shares nearly tripled on their trading debut last November valuing it as the world's fifth-biggest Internet firm, is due to announce its first-ever results on Tuesday.

The consensus forecast, according to a poll by Reuters, is for a net profit of about HK$850 million ($109.5 million) for the year. ($1=7.761 Hong Kong Dollar) (Reporting by Vinicy Chan and Donny Kwok; Editing by Edmund Klamann)