Insurer Aviva sells U.S. unit for $1.8 billion LONDON (Reuters) - Aviva (AV.L), Britain's No. 2 insurer, has agreed to sell its U.S. business for $1.8 billion, far less than it paid for it and the biggest disposal so far in a reorganization aimed at boosting its underperforming share price. Aviva USA Corporation, a provider of life insurance and annuities, is being bought by Athene Holding, a specialist life insurer majority-owned by U.S. private equity company Apollo, Aviva said on Friday. The sale price is below the $2.9 billion that Aviva paid for the U.S. business in 2006, but the insurer said the deal would make it financially stronger by reducing capital requirements and cutting its exposure to volatile credit investments. Aviva's economic capital surplus - the amount by which its capital reserves exceed its requirements - will rise by 1.1 billion pounds ($1.79 billion), the company said. "The disposal of the U.S. business represents a successful end to the year and sets us up well for 2013," Aviva chairman John McFarlane said in a statement. Aviva shares were down 0.5 percent by 5:55 a.m. ET, against a 0.8 percent fall in the STOXX 600 European insurance share index .SXIP. The stock has risen 27 percent since the start of the year, lagging a 33 percent gain for the sector. The U.S. sale forms part of a plan launched by Aviva in July to sell or close 16 businesses that tie up over a third of the insurer's capital while contributing just 18 percent of operating profit. Aviva has so far also jettisoned part of its stake in Dutch insurer Delta Lloyd (DLL.AS) as well as its entire share of Aseval, a Spanish joint venture with Bankia (BKIA.MC). The reorganization, drawn up by McFarlane, came after investors forced out chief executive Andrew Moss, who had overseen a 60 percent fall in Aviva's share price during his five-year tenure. Mark Wilson, formerly chief executive of Asian life insurer AIA, takes over the top job at Aviva on January 1, the insurer said last month. Aviva USA accounted for about 9 percent of Aviva's total operating profit last year. Proceeds from the sale will be $1.55 billion once debt is repaid, Aviva said. Reporting by Myles Neligan; editing by Huw Jones and Keiron Henderson