LONDON (Reuters) - Aviva (AV.L: Quote, Profile, Research) is in talks to buy U.S. life insurer AmerUs Group (AMH.N: Quote, Profile, Research), valued at about $2.3 billion (1.3 billion pounds), in a deal that would boost Aviva's undersized presence in the booming U.S. market.

Aviva, whose bid for UK rival Prudential (PRU.L: Quote, Profile, Research) was rebuffed in March, has long said it wants to expand in the United States, the world's biggest long-term savings market.

Des Moines, Iowa-based AmerUs, focussed on lucrative indexed annuities, said in a statement on Friday there was no assurance the talks would end in a transaction.

But news of a possible deal -- which Aviva expects to fund with a combination of internal resources, debt and a share issue -- pushed the UK insurer's shares down by more than 3 percent.

"They walked away from Prudential already, so there's a little bit of pressure on them to complete this deal. It won't reflect well on the company if they continue to walk away," analyst Mikir Shah at Fox-Pitt, Kelton said.

"It does mean they will get some U.S. exposure -- they won't get the right product range, the right scale of distribution or scale of business, but it's a first step. As far as I'm concerned it highlights their acquisition appetite."

Aviva, Britain's biggest insurer, had denied press speculation in January that it was poised to buy AmerUs, preferring instead to pursue a merger with Prudential, Britain's second largest insurer, largely for its fast-growing Asia and U.S. operations.

Part of the attraction of Prudential was its Jackson National Life unit, one of the largest U.S. life insurance companies with a strong position in the lucrative variable annuity market. Continued...

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