Microsoft has reportedly told Asian governments that they could face intellectual property rights claims if they use free software such as Linux.
Free software such as Linux threatens Microsoft's dominance
Reuters said chief executive Steve Ballmer told Asian leaders Linux violated at least 228 patents. The Linux community disputes these claims.
Mr Ballmer said countries using Linux which entered the World Trade Organisation would be at risk.
Several companies have been threatened with lawsuits for using Linux.
US firm SCO, the company behind the threats, says Linux includes some code to which it owns rights, although the firm is losing its financial backers and has been reluctant to show any proof of its claims.
Mr Ballmer was speaking at a meeting of Microsoft's Asian Government Leaders Forum in Singapore.
He also said that security fears over the use of Microsoft software were overblown.
"We think our software is far more secure. It is more secure because we stand by it, we fixed it, because we built it. Nobody ever knows who built open-source software," he said.
Open-code software such as Linux is freely available on the internet and easily modified by users.
Singapore's Ministry of Defence recently switched 20,000 of its personal computers from Microsoft's operating platform to open-source software.
China, Japan and South Korea have agreed to work together and develop an Asian version of Linux.
The German city of Munich has decided to switch 14,000 of its personal computers to a Linux-based operating system and Paris is said to have considered a similar move.
The popularity of open-source programs such as Linux, which are essentially free, have grown as firms and countries look to cut costs and limit their dependence on software producers.
Microsoft, the world's largest software maker, has the most to lose should Linux use spread.