Yahoo intends to join OpenSocial, a Google-led alliance that is developing a common set of standards so developers can create programs that run on many social networks and other Web sites, according to a person with direct knowledge of Yahoo’s plans.

Yahoo’s backing, which could be announced as early as this week, would bring a large base of users to the OpenSocial alliance, which is seen as a counterweight to Facebook’s successful courtship of application developers. The alliance, which was announced in the fall, already includes MySpace, Bebo and several other social networking sites.

Yahoo’s participation “would mean that the site with the largest group of users, and with the largest base of registered users, would be joining OpenSocial,” said Charlene Li, an analyst with Forrester Research.

When asked about Yahoo’s OpenSocial plans, a company spokeswoman said: “Yahoo has a rich history of supporting open standards, such as OpenID and Apache Hadoop, as we believe industry collaboration is beneficial to the developer community and the Web as a whole. While we are evaluating OpenSocial as an emerging standard, we do not comment on speculation or rumors.”

Yahoo has said it wants to speed up efforts to open its site to outside developers. Although it is not a social network, Yahoo could benefit from third party “social” applications that allow users to share, say, their favorite photos, music or movies with their friends.

The creators of many of the most popular applications on Facebook have already said they plan to also adapt their programs to conform with the OpenSocial standard.