Apple will launch its revamped MobileMe online service Wednesday night sometime between 6 p.m. and midnight US PDT, the company said in a message posted to the current .Mac site.

"As part of the MobileMe launch, www.mac.com will be taken offline at 6 p.m. PT on Wednesday, July 9th," the message read. "[.Mac] members will be unable to access www.mac.com or any .Mac services during this [maintenance] time with the exception of .Mac Mail accessed via a desktop application, iPhone, or iPod touch."

MobileMe is the replacement for the existing .Mac online sync and data storage service; when introduced last month by Apple executives, it was touted as "Exchange for the rest of us," a reference to the new synchronization features it will offer iPhone users.

The service will provide push sync between Macs, PCs and iPhones, as well as new Web-based e-mail, contact and scheduling applications. Apple will also boost the online storage allowance from 10GB to 20GB. The annual fee will remain US$99.

"MobileMe will be available as soon as possible during this [Wednesday] maintenance window," Apple said.

The service's Wednesday roll-out is one of the steps Apple must take before the debut of the iPhone 3G later this week. Although the new iPhone won't go on sale in the US until Friday at 8 a.m. local time, mobile carriers in other countries will start selling Apple's smart phone earlier.

SoftBank Mobile Corp., for example, will put the iPhone 3G on sale at its store in Tokyo's Harajuku district at 7 a.m. local time on Friday, which is 6 p.m. Thursday, July 10, in the Eastern time zone of the US.

Also expected to out before Friday is an update to iTunes, Apple's online music and video store, which will add access to the App Store, the online mart for downloadable iPhone applications, to its offerings.