UPDATE 1-Climate investor group seeks to shore up support after US exits

The world's biggest climate investor group has told members its approach does not breach U.S. antitrust and securities law, according to letters seen by Reuters on Thursday, as leaders seek to shore up support days after the shock exit of several large firms. Climate Action 100+ was rocked last week by the withdrawal of the fund arms of State Street and JPMorgan and bond giant Pimco, while the world's largest asset manager BlackRock scaled back its involvement. In a letter to members on Wednesday, one of the five investor networks coordinating CA100+, the Principles for Responsible Investment (PRI), urged members to stand firm despite the departure of what it described as "a small number of members", and addressed legal concerns.