According to information forwarded by sources 'in the know', the three-year-old San Francisco, California-based Internet-messaging company Twitter is on its way towards an estimated $1 billion total value - with the almost done deal for $100 million in new funding!

It is believed that the funding round will witness the participation of private-equity firm Insight Venture Partners, and mutual-fund biggie T. Rowe Price Group as new investors, over and above the existing Twitter investors - including Spark Capital and Institutional Venture Partners.

Though Twitter has yet to make money, the investors' valuation of the company at nearly $1 billion - more than three times the valuation Twitter received during its February capital raising round - underscores the fact that the popular microblogging service, which enables users to send out brief 140-character messages, has shown notable growth.

Going by comScore statistics, Twitter, led by CEO Evan Williams and co-founder Biz Stone, has grown from 4.3 million unique visitors worldwide in August 2008 to 54.7 million visitors in August this year. The company, which had 45 employees in May, recently hired some senior employees from Google and other companies.

With the valuation of the service - which is still struggling to develop a business model - increasing by leaps and bounds, Twitter executives have reiterated their commitment to building an independent and sustainable business, thereby making its imminent acquisition less likely!