The part Apple is offering to replace is an "Ultracompact USB power adapter" reportedly included with iPhone 3G models sold in Japan, Canada, Mexico, the United States and a half dozen South American countries.
"Customer safety is always Apple's top priority, and therefore we have voluntarily decided to exchange every Ultracompact power adapter for a new, redesigned adapter, free of charge," Apple said.
Apple advises iPhone 3G owners to charge their handsets by plugging them into computers or with a standard-sized Apple power adapter until the potentially problematic part is replaced.
Instructions for getting Apple adapters replaced were posted online at www.apple.com/support/usbadapter/exchangeprogram/.