TOKYO (Reuters) - U.S. fund Artisan Partners Asset Management ( APAM ) ramped up pressure on Japan's Seven and i holdings ( SVNDF ), calling on the board to provide an update on a takeover bid from Canada's Alimentation Couche-Tard ( ANCTF ) by Sept. 19.

In a letter dated Friday and sent to journalists, Artisan portfolio managers N. David Samra and Benjamin L. Herrick recommended that Seven & i ( SVNDF ), operator of the 7-Eleven convenience store chain in Japan, seriously consider ACT's offer, and to solicit offers for the company's Japanese subsidiaries "as quickly as possible."

"ACT is uniquely positioned to enhance (Seven & i's ( SVNDF )) corporate value," Samra and Herrick wrote.

"Negotiating with ACT is the best tactic to preserve positive stakeholder outcomes in Japan," they said. "It is imperative that the board of directors negotiate with ACT immediately to achieve the best possible outcome for shareholders."

Artisan's letter, which was highly critical of Seven & i's ( SVNDF ) track record of enhancing corporate value, highlights the pressure on the company from shareholders over the potential deal, which would likely be the biggest-ever overseas buyout of a Japanese firm.

ACT, which is the owner of Circle-K convenience stores, last week said it had approached Seven & i ( SVNDF ) about a possible acquisition, without disclosing a potential deal value.

Artisan has been a critic of Seven & i's ( SVNDF ) management and structure since 2019, when the letter says it became a shareholder. It said it is an active - not activist - shareholder, which engages with corporate management and boards. (This story has been corrected to fix the spelling of 'alimentation,' in paragraph 1)