Google is joining a consortium to build a trans-Pacific fiber-optic cable, yet another sign that Internet companies are becoming powerful communications entities in their own right as users increasingly turn to the Web to swap videos and talk across the globe.

The move, which was announced Monday afternoon, is the first time an Internet company has invested in a cable spanning an ocean, said Alan Mauldin, research director with Washington-based research firm TeleGeography.

The 6,200-mile cable, which is estimated to cost about $300 million, is being funded by six companies that, in addition to Google, include telecommunications companies Bharti Airtel in India and SingTel of Singapore, and Pacnet, a Hong Kong-based deep-sea fiber-optic cable network operator.