The ceasefire, signed separately by the Tamil Tiger chieftain and Sri Lanka's then premier, came into effect on February 23, 2002.
It led to direct negotiations and optimism that real peace would take hold after decades of bloodshed.
However, six rounds of talks which started in September 2002 ended in March 2003. Attempts to revive them last year failed despite two face-to-face encounters in Switzerland.
"We don't have a ceasefire today even though both sides have said they are committed to upholding it," said Sunanda Deshapriya, director of the private Centre for Policy Alternatives think-tank. "There is an undeclared war."
"There is no life left in this ceasefire. If at all, the parties will have to negotiate a fresh deal," Deshapriya added.
Official military estimates show that nearly 4,000 people have been killed in a new wave of fighting over the last year after the guerrillas threatened a return to full-scale conflict unless they were offered a power-sharing deal.