Microsoft chief executive officer Steve Ballmer has mocked Google's entry to the mobile phone software market, questioning its strategy of giving away its software.

The first Google smartphone, the G1, was recently launched by German telco T-Mobile. Most smartphones and personal digital assistants use commercial operating systems such as Symbian or Microsoft's Windows Mobile, but the G1 uses Google's open-source Android.

Mr Ballmer, in Sydney for Telstra's annual investor briefing, said Google would not have an "easy" time convincing phone makers to switch to Android.