An effort in the U.S. Senate to expand the Federal Bureau of Investigation's authority to use a secretive surveillance order has delayed a vote on a popular email privacy bill, casting further doubt on whether the legislation will become law this year.

The Senate Judiciary Committee on Thursday postponed consideration of a measure that would require government authorities to obtain a search warrant before asking technology companies, such as Microsoft and Google, to hand over old email messages. A version of the Senate bill unanimously passed the House last month.

Currently, federal agencies do not need a warrant to access emails or other digital communications more than 180 days old due to a provision in a 1986 law that considers them abandoned by the owner.