Microblogging service Twitter is working on an $800 million funding deal that values the company at $8 billion, the website All Things D reported.

The funding round would be completed in the next several weeks, according to the site.

The deal would comprise two parts: a $400 million investment in Twitter and $400 million to cash out existing investors and employees.

A Twitter spokeswoman said the company does not comment on financing.

The new valuation would be more than double Twitter's valuation when it last raised cash in December. Then, it raised $200 million at a valuation of $3.7 billion in a deal led by Kleiner Perkins.

Twitter is currently working to build revenue, primarily through advertising.

The company only began offering advertising on its service in April 2010 and is expected to generate about $150 million in ad revenue this year, according to estimates by research firm eMarketer.

That is low compared with other social networking companies. Revenue at professional social network LinkedIn, for example, totaled $243 million last year.

Twitter Chief Executive Dick Costolo called secondary markets a distraction on Tuesday. Speaking at a conference in Aspen, he said he expects private companies will increasingly enact policies to restrict the trading of their shares on those unregulated exchanges.

(Reporting by Sarah McBride; Editing by Gary Hill)

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