ICANT, the organisation responsible for allocating internet addresses, will switch off the present IPv4 addressing system in 30 days, leaving only websites that support the new IPv6 accessible to internet users.
The move is an effort to speed up conversion to the new IPv6 scheme, which offers billions more addresses than IPv4.
"We have only 10,000 addresses left in IPv4, and those are allocated to Tuvalu [a remote group of Pacific islands] so the internet will effectively run out of addresses unless we all make the change," a spokeswoman said.
She said uptake of the new IPv6 addressing scheme was too slow. "Switching off IPv4 will ensure that more websites convert quickly to IPv6. We all know that it's in the web's best interests, so if we have to do it, we might as well do it sooner rather than later."
Spokesmen for Cisco and Juniper Networks, which provide most of the network routers, were stunned by the news.
"We are still testing IPv6, so this has come like a bolt from the blue," Cisco said.
Juniper Networks said it was scrambling its factory to take advantage of Cisco's position. "We are still in beta, but the factories are up and running," a spokesman said. "If Google and Microsoft can get away with releasing beta code, we can too."
A Google spokesman was guarded in his response. "We expect to have a window of opportunity before the Great Firewall of China starts blocking our IPv6 service," he said. "But it's going to play hell with search on the old system."
Google and others called for the decision to be rescinded, but ICANT was adamant. "The Terminator might be back, but we're not," she said.