TOKYO, June 20 Reuters Nippon Steel39;s proposed acquisition of U.S. Steel risks raising decarbonisation costs for Japan39;s top steelmaker, an activist shareholder group said, urging the company to address the takeover39;s impact on its climate goals.

Nippon Steel, the world39;s fourth biggest steelmaker, last year announced a 15 billion takeover offer for U.S. Steel, which backed the bid, but has faced resistance from a powerful labour union and the White House.

The potential addition of U.S. Steel39;s 11 blast furnaces to Nippon Steel39;s operations will almost certainly increase the cost of decarbonisation for the company, Brynn O39;Brien, executive director of the Australasian Centre for Corporate Responsibility ACCR, said.

ACCR, which has less than 1 of Nippon Steel39;s shares, has filed shareholder proposals with two other stakeholders, Corporate Action Japan CAJ and Legal General Investment Management LGIM, calling on the company to improve its decarbonisation strategy.

Asked about ACCR39;s concerns, Nippon Steel said in a statement to Reuters it planned to share technologies related to decarbonisation, including hydrogen injection into blast furnaces, with U.S. Steel should the deal close.

The combination of the technologies developed by Nippon Steel and U.S. Steel to accelerate efforts to become carbon neutral by 2050, Nippon Steel said without giving details.

The companies plan to close transaction before yearend.

Nippon Steel holds its annual…