Mayor Bloomberg yesterday questioned a plan to commit to investing $1 billion of teacher pension funds in post-Sandy rebuilding projects, cautioning that shortfalls in returns would be borne by taxpayers.

Comptroller John Liu, ex-President Bill Clinton and the teachers union this week announced a plan to invest in infrastructure projects from the $46 billion Teachers Retirement System.

TRS’s seven-person board will vote on the policy next week, said a Bloomberg aide.