TOKYO (Reuters) -U.S. fund Artisan Partners urged the board of Seven & i Holdings ( SVNDF ) to allow Canada's Alimentation Couche-Tard ( ANCTF ) to conduct due diligence and negotiate a purchase price in its bid to take over the Japanese retail company.

In a letter dated Oct. 15, Artisan portfolio managers David Samra and Benjamin Herrick said a restructuring plan announced by Seven & i ( SVNDF ) last week was "too little, too late".

"The price currently being offered by ACT is clearly superior to the speculative value that could potentially be achieved by implementing the restructuring plan at this late date," they said in the letter.

Seven & i ( SVNDF ) was not immediately available for comment.

At its second-quarter earnings last week, Seven & i ( SVNDF ) unveiled a plan to bundle some of its vast network of non-core assets into a holding company for which it will bring in strategic investors.

The Canadian company announced a preliminary bid for Seven & i ( SVNDF ) in August, and sources said last week it has since hiked its offer by 22% to around $47 billion. If the deal goes ahead, it would be the largest ever overseas buyout of a Japanese firm.

Artisan's letter also urged Seven & i ( SVNDF ) to allow ACT access to conduct due diligence and negotiate a price that maximises value for shareholders.

Artisan had previously sent a letter to Seven & i ( SVNDF ) in August calling on the firm to consider ACT's initial, lower offer as well as solicit offers for the company's Japanese subsidiaries.

Artisan holds 1.11% of Seven & i's ( SVNDF ) outstanding shares, LSEG data showed.

(Reporting by Rocky Swift; Editing by Muralikumar Anantharaman)