COLOMBO, Sri Lanka - Sri Lanka's separatist Tamil Tiger rebels said Monday that they are ready for a ceasefire with the government but told the United Nations in a letter that they refuse to lay down their weapons.
  
The government, however, has rejected the offer, saying the rebels are trying to "save their miserable skins."

In recent months, the rebels have suffered unprecedented military defeats, losing most of their strongholds to government forces. They are boxed into a tiny sliver of land in the northeast along with tens of thousands of civilians. The government says it will soon take the remaining rebel territory.

The Tamil Tigers' political chief, Balasingham Nadesan, said in the letter to the UN that international calls for the rebels to lay down their arms are "not helpful for resolving the conflict" and that the weapons "are the protective shield of the Tamil people and their tool for political liberation."

"We are ready to discuss, co-operate, and work together in all their efforts to bring an immediate ceasefire and work towards a political settlement," Nadesan wrote in the letter to the UN, which also was sent to Britain, Japan, Norway and the United States.

President Mahinda Rajapaksa has rejected past calls for a ceasefire, saying his government will only accept an unconditional surrender by the Tamil Tigers.

"Instead of surrendering as the entire international community and the Sri Lankan government has called them to do, (the rebels) are calling the very people who have asked them to surrender, to save their miserable skins," Foreign Secretary Palitha Kohona said Monday in response to the rebel letter.

In his letter, Nadesan also urged the international community to reconsider their opposition to an independent state for Sri Lanka's ethnic minority Tamils, for which the rebels have fought more than 25 years. Ethnic majority Sinhalese have long dominated the nation's government.

The international community "must re-examine our point that an independent state is the only permanent solution to the Tamil-Sinhala conflict," he wrote.

Jehan Perera, a political analyst from the National Peace Council, said he was not surprised the government rejected the rebel call for a cease-fire.

He said it was a sign the rebels were trying "everything militarily and politically" to stave off defeat.

Human Rights Watch said last week that some 2,000 civilians have been killed in recent months and accused both sides of committing war crimes.

John Holmes, the top UN humanitarian official, has called on both sides to avoid a final "blood bath."

Last Friday, the rebels used two light aircraft in a daring suicide attack targeting the country's air force headquarters and an air base. The government said it shot down the planes before they could reach their targets.

More than 70,000 people have been killed in the civil war.