Twitter is closing a round of funding that will value the company known for its 140-character, stream-of-consciousness blogs at $1 billion, technology news site TechCrunch reported on Wednesday.

The company will raise around $50 million, and Chief Executive Evan Williams told employees about the funding round, TechCrunch said, citing multiple unnamed sources.

A February round of funding led by Benchmark capital had valued the company at around $250 million, TechCrunch said.

Twitter and other social networking sites have been hard-pressed to show that they are viable businesses and that they have what it takes to eventually make a successful public offering or private sale.

The Twitter funding news would raise the industry's credibility with investors, as did a Tuesday announcement from Facebook that it was making enough money to cover expenses.

Twitter's Tweets are 140-character text messages published to subscribers known as 'followers', and the service has become a phenomenon among news junkies, Hollywood watchers -- and many investors.

Both U.S. President Barack Obama and Senator John McCain used Twitter to communicate with voters in the 2008 presidential campaign.

Twitter's key technology is real-time search that lets anyone search the thoughts and ruminations of the Twitter crowd on a moment-by-moment basis. By comparison, Google Inc's search of the entire Web is based on slightly dated information.

Google Chief Executive Eric Schmidt has referred to Twitter as poor man's email. Twitter's co-founder, Biz Stone, has said he would welcome any opportunity to work with Google.

Twitter did not immediately respond to a call seeking comment.

(Reporting by Alexei Oreskovic and Peter Henderson; Editing Bernard Orr, Leslie Gevirtz)