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By Anton Bridge

TOKYO, Dec 11 (Reuters) - Nippon Life Insurance

said on Wednesday it plans to acquire all the shares it does not own in Resolution Life Group Holdings for about $8.2 billion as it pursues growth in the U.S. market.

The all-cash deal represents the biggest overseas acquisition by a Japanese insurer, according to LSEG data.

Nippon Life currently owns about 23% of Bermuda-based Resolution Life and aims to make it a wholly owned subsidiary in the second half of 2025.

It also said on Wednesday it agreed to acquire the remaining 20% stake it does not own in MLC Life from National Australia Bank for about A$500 million ($320 million) and integrate it with Resolution Life Australia.

The deals are the latest example of heavyweight Japanese insurance companies seeking to expand abroad given limited growth prospects at home due to a shrinking and ageing population.

The Resolution Life acquisition would mark Nippon Life's second major overseas investment plan this year, following its $3.8 billion purchase of a 20% stake in U.S. insurance firm Corebridge Financial in May.

It has also sought to diversify its domestic business, buying nursing care provider Nichii Holdings for $1.4 billion in November last year, but it has lagged other Japanese insurers in U.S. acquisitions.

Property and casualty insurer Tokio Marine Holdings bought speciality insurer HCC Insurance Holdings for $7.5 billion in 2015, paid $2.7 billion in 2011 for Delphi Financial and bought Philadelphia Consolidated for $4.7 billion in 2008.

Cross-border M&A involving Japanese companies has surged this year, driven by amended guidelines designed to encourage takeovers of Japanese firms.

Resolution Life is a closed-book insurer that purchases existing insurance policies from insurers in the U.S. and other countries.

($1 = 1.5672 Australian dollars)

(Reporting by Anton Bridge; Additional reporting by Satoshi Sugiyama, Mariko Katsumura in Tokyo and Harshita Meenaktshi in Bengaluru; editing by Chang-Ran Kim and Edwina Gibbs)

((ran.kim@thomsonreuters.com; +81-3-4520-1228;))