(BLOOMBERG) — Apple Inc. plans to debut a smaller, cheaper iPad by year-end, two people with knowledge of the plans have said, to help maintain dominance of the tablet market as Google Inc. and Microsoft Corp. prepare competing hand-held devices.The new model will have a screen that’s seven to eight inches diagonally, less than the current 9.7-inch version, said the sources, who asked not to be identified because Apple hasn’t made its plans public. The product, which Apple may announce by October, won’t have the high-definition screen featured on the iPad that was released in March, one of the sources said.A smaller, less expensive iPad could undercut the ambitions of Google, Microsoft and Amazon.com Inc. to gain traction in the advancing tablet market, said Shaw Wu, an analyst at Sterne Agee & Leach Inc. The new device will probably have a price closer to Google’s Nexus 7 tablet and Amazon’s Kindle Fire, both of which have 7-inch screens and cost $199.“It would be the competitors’ worst nightmare,” Wu said in an interview. “The ball is in Apple’s court.”Trudy Muller, a spokeswoman for Cupertino, California-based Apple, declined to comment.Since the iPad went on sale in April 2010, Apple has dominated the tablet market, which is predicted by DisplaySearch to reach $66.4 billion this year. Apple has 61 percent of the market, according to Gartner Inc.Apple’s rivals are eager to gain a toehold. Google said on June 27 that it will sell a tablet-style device called the Nexus 7. Last month, Microsoft unveiled a tablet called Surface that will have a similar screen size as the current iPad. And Amazon is expected to release a new version of the Kindle Fire later this year.