GOOGLE Inc has thrown its financial clout behind a proposed 563-kilometer underwater electric cable off the east coast in the United States that could form the backbone of a grid carrying power from future offshore wind turbines.

The Internet search company announced the move, which it called an investment in "a superhighway for clean energy" on its corporate blog.

Japan's Marubeni Corp yesterday said it would invest in the project. Google said New York investment firm Good Energies would also take a stake in the project.

Google did not disclose how much it expected the cable undertaking - which would run from Virginia to New Jersey - to cost, but The New York Times reported it as about US$5 billion.

Google and Good Energies officials could not be reached for an immediate comment.

About a dozen offshore wind farms are proposed for the country's east coast.

Offshore wind in the region could generate about 127 gigawatts of power, enough to meet half the current electric demand, according to a recent study by ocean conservation group Oceana.

There are currently no offshore wind farms in the United States, although developers, including Cape Wind and Deepwater Wind, have proposed installations for the waters off Massachusetts, Rhode Island and New Jersey.

The rising interest has attracted the attention of major industrial companies, including General Electric Co, Siemens AG and Vestas, which make wind turbines.

The proposed cable would be installed under the seabed at a distance of 24km to 32km offshore, a distance that would make turbines all but invisible from the coast and head off one of the major complaints that has dogged Cape Wind, which was first proposed in 2001.