The department scheduled an announcement for noon (1600 GMT) on a "significant antitrust matter," according to a statement, which had no additional details.
According to the report, the lawsuit alleges Apple and the major book publishers reached an agreement to cease competing on the retail prices of e-books, to increase prices significantly, and to guarantee Apple a 30 percent commission on each e-book sold.
The daily said a settlement involving some of the publishers is expected to be filed Wednesday, according to a person familiar with the matter.
Prior to the introduction of Apple's iPad in April 2010, online retail giant Amazon, maker of the Kindle e-book reader, sold electronic versions of many new best sellers for $9.99.
But Apple forced a change in pricing for e-books when the iPad emerged as a rival e-book platform, moving publishers to a so-called "agency model" which calls for them to set book prices and for Apple to take a 30 percent cut.
But Apple has received support from the Authors Guild, which contends that Apple helped boost competition against Amazon, which had dominated the market previously.
The five publishers believed to be under investigation were CBS Corp.'s Simon & Schuster, Lagardere SCA's Hachette Book Group, Pearson's Penguin Group (USA); Macmillan, a unit of Verlagsgruppe Georg von Holtzbrinck, and HarperCollins, a unit of News Corp., which owns The Wall Street Journal.
In December European antitrust officials announced they were conducting a probe into Apple and the five publishers to determine whether they had struck illegal deals with "the objective or effect of restricting competition and fixing the price of e-books at a high level in Europe." Also last year, EU competition authorities raided the offices of several companies active in the e-book sector.
Britain's Office of Fair Trading (OFT) had run its own parallel investigation into e-books but closed it after Brussels opened a probe.
Apple and Amazon dominate the e-book market, selling both the readers and the electronic literature to read on them.
Also competing are publisher Barnes and Noble's Nook reader, the Kobo Touch tablet tapped by French retail giant FNAC, and Samsung's new Galaxy Tab. (hurriyetdailynews)