May 27 (Reuters) - The amount of cash flowing into the U.S. Federal Reserve’s reverse repurchase (RRP) facility hit an all-time high of $485 billion on Thursday, further pressuring key short-term interest rates, which could fall below zero. The amount of money cash-heavy financial institutions have been loaning the central bank overnight at 0% interest has been ratcheting higher since March. The record amount accepted by the New York Fed for Thursday’s RRP operation was up from Wednesday’s $450 billion and exceeded a previous high of $474.6 billion on Dec. 31, 2015, according to data from TD Securities. The Fed launched its reverse repo program in 2013 to soak up extra cash in the repo market and create a strict floor under market rates, particularly its policy rate. Eligible counterparties lend cash to the Fed in return for Treasury collateral on an overnight basis. (Reporting By Karen Pierog) Our Standards: The Thomson Reuters Trust Principles.