UPS Inc. said today it has added 23 countries and territories to its "Worldwide Express" service, which guarantees deliveries on the next possible business day at three different time intervals.

The new markets include Vietnam, Saudi Arabia, and Colombia, Atlanta-based UPS said. Others include Morocco, Guatemala, Ukraine, Honduras, Sri Lanka, and a number of Caribbean island nations, UPS said.

Under the service, deliveries are made the next business day by 10: 30 a.m., noon, or 2 p.m., depending on the destination. UPS said. Until now, deliveries to the 23 new markets were guaranteed by the end of the next business day.

Kyle Peterson, a UPS spokesman, said the service's delivery windows are between one and three days, depending on the location. "When a customer tells us the destination, we tell them how long it will take to get there," Peterson said in an e-mail. "At that time, we will lock in the delivery time, which is guaranteed." Peterson declined to comment on UPS' success rate in hitting the service's next-day delivery targets, saying the information is proprietary.

With the additions, the Worldwide Express service is available in 88 countries and territories, UPS said. Worldwide Express is part of the company's broader "UPS Express" service, which reaches 220 countries and territories with deliveries by the end of the next business day.