ATLANTA — UPS Inc. expects its busiest day overall for shipping packages this year will be Dec. 18.

For the first time since it went public in 1999, the Atlanta-based company is forecasting how many packages it will ship that day. United Parcel Service also will not project how many seasonal employees it will hire this year to help it through the holiday shipping season that runs from Thanksgiving until Christmas.

The decision was prompted by weak October retail sales and the uncertainty of the upcoming holiday season amid the worst financial crisis to hit the U.S. in decades.

Last year, UPS, the world's largest shipping carrier, delivered more than 22 million packages on its peak shipping day, which was Dec. 19, and it hired about 60,000 seasonal employees.