The US patent and trademark office, in a setback for Twitter's co-founder Biz Stone, has declined the request of Twitter, applied last month, for ownership of the world 'tweet'; adding that many companies have already applied for patent rights of similar names before the office.

The authority has got applications seeking patent of TweetMarks, Cotweet and Tweetphoto, which seems quite similar words and would lead to confusion in future. Technology blogger, Sam Johnston, wrote in his blog that there are three applications pending with the office seeking patent for 'tweet' word.

Social networking site, Twitter, launched three years back, has become a respectable and popular name over internet and has been recently included in the Associated Press's style guide as a verb. Similarly, Australia's Macquarie dictionary too added the word, given its immense popularity.

Mr. Biz stone said: "We have applied to trademark tweet because it is clearly attached to Twitter from a brand perspective but we have no intention of 'going after' the wonderful applications and services that use the word in their name when associated with Twitter."