Google Inc. said late Friday that it objected to Taiwanese PC maker Acer Inc.'s development of a smartphone that is powered by a rival mobile operating system, the launch of which was delayed this week.

Acer postponed the launch of the phone, which runs the Aliyun mobile operating system made by China-based Alibaba Group Holding Ltd.

More than 90% of Acer's smartphones are powered by Google's Android mobile operating system.

Google responded to allegations it stopped the launch of a new Acer smartphone in China, by stating that the handset's Chinese-developed mobile OS was "apparently derived" from Android, but still not fully compatible with the Android ecosystem and its apps.

 Acer was originally scheduled to launch a new smartphone on Thursday that was to use the Aliyun OS, a Linux-based mobile operating system developed by a subsidiary of Chinese e-commerce giant Alibaba Group. But the launch event for the device was abruptly canceled, with no clear word from Acer on why.

Alibaba, however, quickly responded and alleged that Google had threatened to revoke Acer's license to use Android if it went ahead with the launch of the Aliyun OS smartphone.

The Google led Open Handset Alliance, of which Acer is a member, is meant to promote the development of Android. Members are restricted from building handsets that use incompatible versions of Android.

A Google spokesman also confirmed that the company did indeed alert Acer that it was launching a phone using an allegedly incompatible version of Android. But the spokesman declined to offer specifics and if Google threatened to revoke Acer's license to use Android.

Alibaba strongly disagreed with Google's comments. John Spelich, Alibaba's vice president of international corporate affairs, said in a statement, "Aliyun OS is not part of the Android ecosystem so of course Aliyun OS is not and does not have to be compatible with Android."

Alibaba has previously said that Aliyun is based on Linux "open source" software, or software that is free for anyone to use. Android is also based on Linux software.

For Alibaba, part of the incentive for developing Aliyun came from the expected migration of online shoppers from PCs to mobile devices, Mr. Zeng said.

According to research firm IDC, China's smartphone market is set to overtake the U.S. market as the world's largest by the end of the year.