BlackRock Inc. warned that public pensions are at risk from Democrats and Republicans pressing asset managers to heed their political demands over how retirement funds are invested.

The officials’ requests are part of “a concerning trend by both parties of politicizing the management of public pension funds,” S. Jane Moffat, BlackRock’s head of state and local government affairs and public policy, said in a letter Wednesday. “The politicization of pension fund management ultimately costs savers and retirees.”