WELLINGTON, New Zealand—Three New Zealand telecommunications companies say they plan to jointly build a new $60 million fiber-optic cable connecting New Zealand with Australia.

Telecom, Vodafone and Telstra announced Tuesday they hope to complete the undersea Internet-powering cable by the end of next year. They say its capacity of 30 terabits per second is about 300 times New Zealand's data needs. The companies say it will improve the country's notoriously slow Internet speed and boost the economy.

