Updated

A group of Somali pirates who have hijacked a tanker loaded with military supplies say they will fight to the death before giving in to Russian and U.S. authorities.

The superpowers have been unable to end the standoff and remain concerned that the ship's cargo of 33 tanks and other weapons could fall into enemy hands.

But a local official reported that the pirates turned down a demand from Islamist insurgents for some of the arms.

The tense situation off the coast of Somalia began 11 days ago when the pirates took control of the Ukrainian vessel MV Faina.

They have asked for a ransom of about $22 million, or 11 million British pounds, to release the 21 Ukrainian, Latvian and Russian hostages and the cargo.

"If we are attacked we will defend ourselves until every last one of us dies," Sugule Ali, a spokesman for the pirates, said in an interview over satellite telephone from the ship.

"We only need money and if we are paid, then everything will be OK," he said. "No one can tell us what to do."

Ali's words came as U.S. warships continued to surround the ship and American helicopters buzzed overhead.

A Russian frigate is also expected to arrive within days.

It may come as some comfort to authorities that the group reportedly refused to hand over arms to the al Shabaab group, which opposes Somalia's interim government.

But the outcome of the stand-off remains uncertain.

Somali pirates have seized more that 30 vessels off the coast of their country so far this year.

They have received ransoms of between $20 million and $32 million, according to a report by British think tank Chatham House released earlier this week.

Residents confirmed fears that ransom payments to pirates were being passed onto the Islamist movement and were fueling the insurgency against President Abdullahi Yusuf's government.

But despite the frequency of such incidents, pirates rarely hurt their hostages.

One Russian has reportedly died aboard the Faina, apparently of illness.