Halliburton Co , the world's second-largest oilfield services company, on Wednesday reported higher quarterly profits as North American sales reached a record high, lifting its shares in premarket trading.

First-quarter profit rose to $627 million, or 68 cents per share, from $511 million, or 56 cents per share, a year ago.

Excluding one-time items such as a $300 million charge for estimated losses from the BP Plc Gulf of Mexico oil spill two years ago, Halliburton's earnings per share of 89 cents topped the average analyst estimate of 85 cents, according to Thomson Reuters I/B/E/S.

Chief Executive Officer Dave Lesar said the record North American revenue of $4.2 billion came as new oil drilling activity in the United States helped offset a drop in natural gas drilling.

But Lesar warned that weak U.S. natural gas prices, which have fallen to their lowest level in a decade, and the disruptions caused by shifting supply chains, would contribute to lower margins in the region in the second quarter.

Halliburton is heavily exposed to the U.S. market relative to larger rival Schlumberger , which earned about two-fifths of its 2011 income in North America, compared with more than three-quarters for Halliburton.

Halliburton is the market leader in pressure pumping, used in hydraulic fracturing to extract oil and gas from shale. New technology has opened up new sources that are likely to keep prices low for years.

Its revenue rose 30 percent to $6.9 billion.

Halliburton's shares rose 1.7 percent in premarket trading to $33.20.

(Reporting by Matt Daily in New York and Braden Reddall in San Francisco; Editing by Maureen Bavdek)