Internet and telephone users in Asia will have to wait at least another week before systems hit by last month's earthquake are back to normal.
Internet services have been disrupted across Asia
Work is getting under way on undersea telecommunications cables which were damaged by the quake off Taiwan.
A UK firm involved in the work said most repairs should be completed in a week to 10 days.
Traffic was switched away from the cables after the quake, but connections have been slower than normal.
The magnitude 7.1 earthquake on 26 December badly damaged some eight submarine optic fibre cables on the seafloor of the Bashi channel between Taiwan and the Philippines.
The cables serve Taiwan, Hong Kong, China, South Korea and Japan - all of whom suffered severe disruption to their internet and telephone networks.
UK-based Global Marine Systems is sending three of some six or seven ships that will work on retrieving the cables from the 4,000m deep sea bed and fixing them.
The firm's regional director, Ian Douglas, said the earthquake had caused an unprecedented level of damage to the cables.
"Twenty-one support cable faults occurred. That's more than we would expect to see across the whole of Asia in 12 months," he told the BBC News website.
He said the job would be extremely difficult as some cables had become trapped under the seabed or were tangled up.
"The very deep water is beyond the limits of the unmanned subs that we would normally have used," he said.
"Instead, we must use a kind of grappling hook - a rope with chains and hooks attached - that can be dragged along the sea bed to try and find the cable."
He said, in some cases, up to 100km of cable may have been buried or damaged.
Despite the difficulties, Mr Douglas said that by next Monday "we hope enough cables are restored so that there will not be the current degradation in internet speeds."
He predicted it would take a week to 10 days to correct most of the faults.
Telecoms operators routed services through other means such as overland cables after the undersea cables were hit.
But millions of internet and phone users from South Korea to Hong Kong have continued to encounter problems and delays.