In a statement, ETA said it had not yet had any direct contact with the government since declaring a truce three months ago.

The announcement comes three days after Prime Minister Jose Maria Aznar authorised the transfer of 21 ETA prisoners - described as ''the worst of the worst'' - to jails closer to home.

They are due to be moved on Tuesday from prisons on the Canary Islands, the Balearics and Spain's North African outposts.

But Basque nationalist politicians have dismissed the government's gesture as insufficient.

The transfer of prisoners is one of ETA's main demands - it wants more than 500 moved closer to the Basque region in time for Christmas.

The organisation is blamed for nearly 800 killings in its 30-year-old battle for an independent Basque homeland in northern Spain.

It began an open-ended, unconditional ceasefire in September.

But Mr Aznar has said the group must do more to show commitment to permanent peace before substantial negotiations begin.

ETA keeps weapons for self defence

In its three-page announcement written in the Basque language, ETA made no mention of a permanent ceasefire or laying down its arms - both key government requirements.

"We will continue the indefinite truce. But until we reach an agreement with the Spanish Government, we will not announce a definitive ceasefire," it said.

In September, ETA said it reserved the right to keep its weapons for self-defence.

But when the Spanish Government offered to start talks with the guerrilla's allies, ETA said it was considering a "definitive end" to its armed campaign.

ETA killer released early

Meanwhile, the government has reportedly released ETA's longest serving prisoner.

Mikel Sarasketa, 43, has been freed conditionally half way into his 41-year term, according to the Spanish news agency Efe.

He was serving the bulk of his sentence for his role in the killing of three policemen in a San Sebastian bar in 1978.

Mr Sarasketa was released on humanitarian grounds after suffering epileptic attacks and a brain haemorrhage.