SEOUL » Samsung Electronics Co. said Wednesday its latest Galaxy Note 4 smartphone will go on sale in China and South Korea later this week as its flagging mobile business tries to defend sales from Apple’s new iPhones.

Samsung said all three Chinese mobile carriers and all three South Korean mobile operators will begin Galaxy Note 4 sales on Friday.

Samsung’s announcement marks the first time the Korean company has released a flagship smartphone in China before other markets.

Apple’s iPhone 6 has yet to arrive in China, the world’s most populous country. But Apple Inc. still chalked up 10 million sales of the iPhone 6 and 6 Plus models in the first three days after the phones went on sale.

Samsung’s early move in China comes as the South Korean company faces challenges on multiple fronts. Its profit from the crucial mobile business has flagged and local brands in India and China have dented its sales of cheap phones.

Apple’s new iPhone 6 with its larger screen than previous models eliminates at key advantage for Samsung that lured buyers with the big screens of its Galaxy phones.

The 4.7-inch screen of the iPhone 5 has been increased to 5.5-inches for the iPhone 6 Plus.

The Galaxy Note 4’s display measures 5.7 inches diagonally, slightly larger than the biggest iPhone. The Note series comes with a stylus that Samsung calls "S Pen" for note taking and drawing.

Samsung moved forward its launch schedule for the new Note phone from October after Apple announced the iPhone 6 with a bigger screen.

U.S. sales of the Galaxy Note 4 will start on Oct. 17.

Samsung said the Galaxy Note Edge, which has a curved side screen that serves as a second screen to display weather information, clocks and menu buttons, will start going on sale in late October.