Prabhakaran said the war was spreading and becoming more intense
The leader of the Tamil Tiger rebels in Sri Lanka has said that the government is living in "dreamland" if it expects outright military victory.
In his annual speech, Velupillai Prabhakaran said that it was "a dream from which they would soon awake".
The speech was made as the army says it is on the verge of capturing the rebels' de facto capital, Kilinochchi.
Defence Ministry spokesman Keheliya Rambukwella described the speech a "cry from the deathbed".
In an interview with the BBC Sinhala service, he called on Mr Prabhakaran to lay down his arms in order to stop "bringing disaster to the Tamil people".
Meanwhile the air force says it attacked a radio station belonging to the Tigers shortly before the speech.
The rebels said that equipment and buildings were damaged in the raid, but did not say whether there were any casualties.
An air force spokesman said the rebels' communication centre had been destroyed, but correspondents say it did not stop Mr Prabhakaran's speech being broadcast on radio and the internet.
KEY DATES IN THE WAR
1983: 13 soldiers killed in one of the first rebel attacks
1990: Indian troops leave after unsuccessful peacekeeping mission
1991: Tamil Tigers assassinate Indian PM Rajiv Gandhi
1993: President Premadasa killed in Tamil Tiger attack
1998: Rebels capture Kilinochchi
2000: Rebels capture key Elephant Pass base
2001: Rebel attack on Colombo airport
2002: Ceasefire leads to inconclusive peace talks
2005-2008: Fighting intensifies in north and east
Mr Prabhakaran accused the government of being "committed to a military solution".
He said that the war was becoming "intense and widespread" and that the government was "executing its war plan at full gallop".
"But our freedom fighters have dedicated themselves to unbending resistance against this war of aggression... with various countries of the world buttressing the genocidal war... we are waging a defensive war for the freedom of our people.
"We have had direct confrontations even against superior powers, stronger than us. We have withstood wave after wave of enemy attacks," he said.
The government says its forces are on the verge of capturing Kilinochchi in northern Sri Lanka. The town is the administrative centre of the territory controlled by the rebels and correspondents say its loss would be a huge setback for them.
The head of the army recently said the rebel leader was now like a "caged animal" and faced certain defeat.
But Mr Prabhakaran appeared to be dismissive of the situation on the battlefield.
"When compared to these happenings of the past, today's challenges are neither novel nor huge. We will face these challenges with the united strength of our people," he said.
"Whatever challenges confront us, whatever contingencies we encounter, whatever forces stand in our path, we will still continue with our struggle for the freedom of the Tamil people."
The Tamil Tiger leader also urged the international community to lift bans on his group - which many countries have banned as a "terrorist" organisation.
Mr Prabhakaran's speech came as skirmishes continued in the north amid heavy monsoon rainfall which correspondents say may have temporarily delayed the army's offensive.
The BBC's Roland Buerk in Colombo says that recent years have been disastrous for the Tamil Tigers.
After a ceasefire broke down in mid-2006 they were driven from the east of Sri Lanka.
Much of their arms smuggling fleet was reported as sunk by the navy and now their territory in the north is crumbling.
Every year the rebel leader makes a policy speech on what the rebels call heroes' day, when they commemorate their dead.