Apple has said its latest iPhone5 is on track to "shatter" its sales record but warned it may not be able to meet stratospheric demand.
The technology giant said more than two million customers had pre-ordered its latest smartphone in the first 24 hours.
That was double the amount for its iPhone 4GS.
Philip Schiller, Apple's senior vice-president of worldwide marketing, said: "iPhone 5 pre-orders have shattered the previous record held by iPhone 4S and the customer response to iPhone 5 has been phenomenal."
The latest device became available for pre-order on 14 September and will go on release this Friday.
But Apple warned that the phenomenal demand had outstripped "initial supply".