(J. Scott Applewhite/AP)

Democratic presidential hopeful Bernie Sanders said Wednesday that the Postal Service caused a “disaster that is negatively impacting Americans all over this country” when it shuttered more than 140 mail-sorting plants and slowed delivery times to cut costs.

“I have heard from people all over this country who have reported serious delays in receiving life-saving prescription drugs, and the bills that they need to pay to keep the lights and electricity on in their homes,” the senator from Vermont wrote in a letter to Postmaster General Megan Brennan, urging her to reinstate overnight delivery for regional mail.

Sanders wrote that he has heard from veterans and seniors in his rural state who are not getting life-saving prescriptions in the mail for nine or even 11 days.

[Post office can’t even meet its own lower standards as mail delays soar]

“This delay means that some of the most vulnerable people in the country are going without the medications they need, or they are being forced to travel long distances because they cannot rely on the timely delivery of mail.”

Sanders, who has opposed proposals by postal officials to close rural post offices and eliminate Saturday delivery, was responding to an urgent alert to the Postal Service this month from the agency’s inspector general that the number of letters arriving late has jumped by almost 50 percent since the start of the year.

[How Bernie Sanders draws huge crowds]

The watchdog is recommending that postal officials put all further closures of mail-sorting plants on hold until service stabilizes. Sanders went further, asking Brennan to restore the overnight delivery standard for regional mail.

He said the Postal Service’s biggest financial obstacle is a Bush administration mandate that the agency prefund future health-care costs for retiring postal workers, a $5 billion a year payment the agency has not made for more than a year.

To cut costs, postal officials have closed about 150 mail-sorting plants since 2012. But in January, they relaxed delivery standards, eliminating overnight delivery for local first-class letters that used to arrive the next day. And up to half of mail traveling longer distances was given an extra day to reach its destination.