The United States Postal Service is refining its service standards, which is sure to impact the speed of deliveries in Illinois.

The service said these changes will improve efficiency and transparency for USPS customers but has admitted that some deliveries will be slowed.

Here's what to know about the service changes and their expected impacts on Illinois customers.

Which mail will be impacted?

The changes will impact First-Class Mail, periodicals, marketing mail, package services, USPS Ground Advantage, Priority Mail, and Priority Mail Express, according to a fact sheet released by the Postal Service.

When will changes be implemented?

Phase one of implementation began on April 1, while phase two is set to start on July 1.

What changes to expect

The USPS said the majority of mail and packages will retain the same service standards, while others will receive faster or slightly slower service. For First-Class Mail, the Postal Service said 75% will be delivered at the same standard, while 14% will be delivered faster and 11% will be delivered slower.

How will rural Illinois customers be affected?

The USPS said in its release that rural customers will benefit from the service changes.

"The majority of mail and package volume, including mail and package volume destined to rural communities, originates in ZIP codes that are within 50 miles of an RPDC," the service said. "This volume will not be impacted by (regional transportation optimization) and can be processed more quickly, as it will no longer need to wait for volume arriving from outlying areas."

How much money will these changes save USPS?

The Postal Service projects these changes will save it at least $36 billion over 10 years from transportation, mail processing and facility cost reductions.

Will the USPS be privatized?

President Donald Trump would need approval from Congress to privatize the USPS, but he said in February that he was considering merging the service with the Commerce Department. Experts said this would not only likely violate federal law but would also lead to post office closures, slower mail delivery and higher service costs, hitting rural areas the hardest.

Letter carriers protested against the rumored privatization in more than 200 cities nationwide on March 23, including in Chicago, Springfield, Carbondale, Peoria, Rockford and Galesburg.

Will USPS employees be laid off in Illinois?

Postmaster General Louis DeJoy sent a letter to Congress in March announcing his plans to cut 10,000 workers and billions of dollars from the USPS budget, but no further details about projected cuts have been released.

The USPS has more than 26,000 employees in Illinois, according to the Federal Reserve Bank of St. Louis.