Oregon Sens. Jeff Merkley and Ron Wyden, Oregon Democrats, were among 24 senators Friday to challenge the U.S. Postal Service postmaster general’s authority to discontinue Saturday mail delivery without congressional approval.

The senators wrote Patrick Donahoe urging him to work with Congress to address the financial challenges facing the post office. The senators also suggested that switching to a five-day service week could lead to further declines in revenue, and that the change would hurt rural communities and middle-class families. In addition, their letter pointed out that the change is a violation of an existing law under the Continuing Appropriations Resolution of 2012.

Stopping mail service on Saturdays would affect 70,000 jobs. The change in service is scheduled to take place later this year.