Prime Minister Gordon Brown said on Wednesday that Britain was ready to help the world's eighth biggest oil exporter deal with unrest in the delta, which has cut Nigeria's output by a fifth and contributed to a rise in global oil prices.

The Movement for the Emancipation of the Niger Delta (MEND), which first launched attacks on the oil industry in early 2006, said Britain was backing an "illegal government" and that it would end a ceasefire at midnight (2300 GMT) on Saturday.

"MEND wishes to sound a stern warning to the British Prime Minister over his recent statement offering to provide military support to the illegal government of (President) Umaru Yar'Adua," the group said in an e-mailed statement.

"Should Gordon Brown make good his threat to support this criminality for the sake of oil, UK citizens and interests in Nigeria will suffer the consequences," it said.

MEND, had declared a unilateral ceasefire on June 24.

Brown, along with other world leaders, is under immense public pressure to try to help curb global oil prices, which surged to a record high above $145 a barrel last week, placing further strain on the fragile world economy.

Bombings of oil pipelines and attacks on installations by MEND have sparked fears of more supply disruptions, increasing nervousness in an already volatile oil market.

Brown said at a Group of Eight summit meeting in Japan that Britain, Nigeria's colonial ruler until 1960, stood ready to give help "to deal with the lawlessness" in the Niger Delta and that he would be meeting Yar'Adua in London next week.

A spokesman for Brown's office on Thursday said the prime minister had not committed to specifically offering military aid. The form of any British help might take, would be the subject of Brown's talks with the Nigerian leader.

BRITONS IN NIGERIA

Britain is one of the largest investors in Nigeria. About 4,000 Britons live in the West African country, many working for large companies including oil and gas firms Royal Dutch Shell, British Gas and Centrica.

The British High Commission in the capital Abuja said it took all threats to British interests seriously. It said Britain's policy on the Niger Delta had not changed.

Yar'Adua has said his administration will take a two-pronged approach to the unrest, pledging development for communities whose land and water has been polluted by oil extraction but also saying he will not tolerate the presence of armed groups.

Vice President Goodluck Jonathan is organising a long-awaited peace summit with the militants, regional governors and oil companies to address the root causes of the unrest, although MEND has said it will not attend.

"We appeal to them to maintain the ceasefire so we can have a peaceful atmosphere for the summit," Jonathan's spokesman, Ima Niboro, said in response to MEND's declaration.