EU regulators are set to accept an offer by Apple and four book publishers allowing Amazon and other retailers to sell e-books more cheaply than Apple to end an antitrust investigation and avoid fines, two sources said on Monday.

Apple, Simon & Schuster, News Corp unit HarperCollins, Lagardere SCA's Hachette Livre, and Verlagsgruppe Georg von Holtzbrinck, the owner of German company Macmillan, made the proposal to the European Commission in September.

The move came after the EU antitrust authority opened an investigation into the companies' e-book pricing model, which critics say prevents Amazon and other retailers from undercutting Apple.

Pearson Plc's Penguin group, which is also under investigation, did not take part in the offer.

The Commission, which in September asked for feedback from rivals and consumers regarding the proposal, has not asked for more concessions, said one of sources.

"The Commission is likely to accept the offer and announce its decision next month," the person said. (Writing by Luke Baker)