NEW YORK CITY (AFP) - Twitter boosted its public stock offering value to as much as US$2 billion (S$2.5 billion), in documents filed Monday.

The regulatory filing raises the share price for the popular messaging platform to a range of US$23 to US$25, from an earlier estimate of US$17 to US$20.

The new share price range would give Twitter a market value between US$12.76 billion and US$13.87 billion.

A date has not been set for initial public offering (IPO) of the big social network, but some reports say it could be as early as this week.

Twitter is offering 70 million shares in most hotly anticipated IPOs since Facebook's last year.

The update filed with the Securities and Exchange Commission also disclosed that IBM is alleging Twitter infringed on three patents, one of several risk factors for the social network.

"Based upon our preliminary review of these patents, we believe we have meritorious defenses to IBM's allegations, although there can be no assurance that we will be successful in defending against these allegations or reaching a business resolution that is satisfactory to us," the document said.