Federal regulators today appealed a judge's ruling that allowed Whole Foods to proceed with its planned $671 million purchase of Wild Oats.

The Federal Trade Commission also asked the appeals court for an emergency stay to block the merger during the appeals processs.

The agency had sought to block the combination of the nation's two biggest natural and organic foods stores, saying it would lead to higher prices and limited selection for customers.

Whole Foods' attorney said he reviewed the judge's 93-page opinion and is confident it will withstand higher court review.

"The opinion is firmly grounded in both the facts and the law, and provides a detailed analysis of 'what is really happening in the marketplace,'" said Paul Denis, a lawyer for Whole Foods.

The entire opinion was filed under seal to protect confidential company information. A version with redacted comments is expected be be made available next week.

Boulder-based Wild Oats shares rose the most in more than five years on optimism that the deal will go through. Wild Oats shares soared $2.74, or 18 percent, to $17.95 in Nasdaq Stock Market trading.