Williams Cos.

(WMB) - Get Report

said its energy-trading arm lost close to half a billion dollars in the second quarter as it was formed to mark down power contracts and provide additional liquidity in the face of ratings downgrades.

The deficit contributed to a second-quarter loss of $349.1 million, or 68 cents a share, at Williams, compared with a profit of $339.5 million, or 69 cents a share, a year earlier. Excluding special items, the company posted a recurring loss in the quarter of 34 cents a share. Analysts on average were expecting a loss of 38 cents.

The Williams division that handles natural gas exploration and transportation posted a second-quarter profit of $131.8 million, compared with $263.9 million during the same period last year.

Williams postponed a conference call to discuss the earnings until later this week.