(Credit: CNET/James Martin)

Apple CEO Tim Cook will testify as part of the U.S. Department of Justice's antitrust case against Apple, a judge ruled today.

Cook, who became Apple's CEO in August 2011, will be required to engage in four hours of testimony per a ruling by U.S. District Judge Denise Cote in Manhattan today, Reuters reports.

Apple had attempted to prevent Cook's involvement, arguing that the Justice Department already had access to nearly a dozen of its executives as part of the case.

In April 2012, the Justice Department sued Apple, along with five of the six largest book publishers in the U.S., accusing all parties of conspiring to set e-book prices and break Amazon's hold on the market with its Kindle e-book reader.

Apple remains the sole defendant in the case, which also targeted News Corp.'s HarperCollins Publishers, Lagardere SCA's Hachette Book Group, Simon & Schuster, Macmillan Publishers (owned by Germany's Verlagsgruppe Georg von Holtzbrinck holding company), and Pearson PLC's Penguin Group. Macmillan, which was the last holdout short of Apple, settled with the Justice Department in early February.

The case is set to go to trial in June.

Apple's battle over e-books