The hotly anticipated event will be Cook's first product introduction since he replaced Steve Jobs last month.
Apple shares have been hitting new all-time highs in anticipation of a strong new product cycle this fall led by the refreshed iPhone 5 and the possibility of a stripped down iPhone 4 to sell in expanding markets like China.
The new iPhone -- which is expected to be redesigned and run on a dual-core processor with a better camera -- is likely to go on sale within two weeks of the announcement.
For Apple fans accustomed to the excitement of Steve Jobs' "one more thing" presentations, there will be a slight adjustment to the lower-key delivery from Cook. In past product showcases when Jobs was unable to attend due to health reasons, marketing chief Phil Schiller stepped in to handle the demos.
Apple shares closed at $413.45 Tuesday after hitting a high of $422.86 earlier in the session. On Wednesday, Apple was up nearly 1% in premarket trading to $415.67.
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