UPDATE 3-Wendy's/Arby's posts loss; Arby's weakness hurts

* Q4 profit 5 cents excluding items meets analysts' view

* Same-store sales up at Wendy's, down at Arby's

* Wendy's and Arby's to combine under one credit agreement

* Shares rise 2 percent (Recasts; adds executive, analyst comment; byline; updates stock movement; Adds Los Angeles to dateline)

By Jessica Wohl and Lisa Baertlein

CHICAGO/LOS ANGELES, March 2 (Reuters) - Wendy's/Arby's Group Inc (WEN.N), the third-largest U.S. fast-food chain, posted a quarterly loss of nearly $400 million on Monday, hurt by impairment charges and falling sales at Arby's sandwich restaurants.

Shares of Wendy's/Arby's, which was formed last fall, rose 2 percent in midday trading after the company also outlined plans to improve performance at its lagging Arby's chain.

The company said fourth-quarter sales at established North American restaurants rose 3.7 percent at Wendy's, but fell 8.5 percent at Arby's -- which has introduced lower-priced sandwiches rather than discount its premium-priced roast beef sandwiches amid intense price competition.

"Arby's clearly needs to hit a home-run to stabilize (same-store sales) declines that are reaching double digits," UBS Equity Research analyst David Palmer wrote in a client note.

Wendy's/Arby's posted a fourth-quarter net loss of $393.2 million, or 84 cents per share, in the company's first financial report of combined results.

The results included $417.9 million, or 89 cents per share, in after-tax charges for writing down the goodwill of Arby's company-owned store operations and for an allowance for doubtful collection for a promissory note received in connection with the company's 2007 sale of Deerfield & Co LLC.

Excluding items, the company earned 5 cents per share, matching the analysts' average forecast, according to Reuters Estimates. Revenue was $896.5 million.

WORKING ON BOTH BRANDS

Arby's owner, Triarc, bought Wendy's International Inc for just over $2 billion in September to form Wendy's/Arby's. Chief Executive Roland Smith is trying to re-establish Wendy's as the fast-food industry's quality leader and is reworking its sandwich buns, french fries and bacon.

Wendy's, which is targeting older customers who already favor the chain, has redone its 99-cent value menu, introducing new products and moving popular items like its chili, baked potatoes and chicken nuggets to higher prices.

That strategy helped boost results at Wendy's, where items from the company's value menu accounted for some 15 percent of overall sales, down from 20 percent about a year ago. Value menu sales are less profitable than other menu items.