The suppliers had planned to start producing the larger screen tablet in mass volume beginning in December, but have been struggling to produce enough new iPhones to keep up with demand, the WSJ said.
Foxconn Technology Co Ltd, which assembles iPhones and iPads, has 200,000 workers in China already putting together new iPhones and making items such as metal casings, the Journal said.
Apple is expected to launch the new iPads at an event on October 16.
Asian suppliers expect Apple's larger tablet, which is rumoured to be called the iPad Pro, to have a 12.9-inch liquid-crystal-display screen with a resolution similar to the iPad Air launched in October last year, the WSJ said.
Previous reports had pegged the iPad Pro to launch in the second quarter of 2015, probably after the anticipated Apple Watch launch.
The 12.9-inch iPad Pro was also tipped to be powered by the Apple A8X SoC, which while not official, does fit in with Apple's tradition of using boosted iPhone chipsets for its iPad tablets, with more powerful GPUs - as was the case with the A5X and A6X chipsets (there was no A7X chipset).
Data research firm IDC said in August that it expected tablet sales to slow globally in 2014.
Apple was not immediately available for comment.
The company said it sold more than 10 million of its new iPhones in the first weekend they were available in September.
Written with inputs from Reuters
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