The policy was scheduled to go into effect this week but drew opposition from flight attendants and federal air marshals worried about security.
The policy also would have allowed passengers to carry bats and other sports equipment, such as ski poles and golf clubs, onto airliners.
The Transportation Security Administration said it wants more feedback from an advisory committee. The delay is temporary, but it is unknown how long it might be.
The U.S. banned all knives from commercial flights after the Sept. 11 attacks.
TSA Administrator John Pistole proposed the policy change last month, saying it would free up the agency to concentrate on protecting against greater threats.
The proposed policy would have permitted folding knives with blades that are 2.36 inches or less in length and are less than 1/2-inch wide.
The policy was aimed at allowing passengers to carry pen knives, corkscrews with small blades and other small knives. TSA screeners confiscate about 2,000 small folding knives from passengers every day.
The Associated Press contributed to this report.