Indian Ocean countries and UN experts have agreed on a timetable for a tsunami early warning system.
The system is needed to avoid a repeat of December's disaster
At a meeting in Paris, delegates decided the system, which could save thousands of lives, would be installed in three stages.
However, the cost of the system and the location of a central tsunami warning office have yet to be decided.
An estimated 300,000 people died when giant waves, set off by an earthquake, laid waste to Indian Ocean coastlines.
Only countries bordering the Pacific Ocean are covered by a tsunami warning system at present.
Experts at the Paris meeting voiced hopes that similar systems could one day be installed across the Mediterranean and the Atlantic Ocean.
In the first, interim step towards a full tsunami warning system, Japan and the US will provide alerts on seismic activity in the Indian Ocean region.
The second step will see tidal movement gauges fitted near Thailand, Indonesia and Malaysia, while 15 such gauges that are already in place will be upgraded.
In the third and final phase, expected to be completed by the end of 2006, a regional warning centre will be built, with links to a network of gauges and underwater sensors across the region.
UN representatives and the Intergovernmental Oceanographic Commission will meet again to work out the cost of the system and the location of the warning centre.
Reid Basher, a senior advisor at the UN's International Strategy for Disaster Reduction, said the new international system would only work if individual nations also trained people in reacting to tsunami warnings.
"Countries still have to get the educational issue resolved," he said.