There was a dramatic new twist to the Indian Ocean pirate stand-off today when the American captain held by Somalis off the African coast attempted to escape by diving into the water.

Captain Richard Phillips, who has been drifting on a lifeboat with his captors for two days, leapt overboard but was retaken by the gang, which is believed to be seeking a ransom for his safe return.

Captain Phillips had been reported to be unharmed after being taken hostage by the four pirates, who failed to capture his 17,000 tonne US-flagged container ship, the Maersk Alabama, on Wednesday. The ship’s lifeboat has run out of fuel, and although two boats full of heavily-armed fellow pirates have taken to sea in solidarity, their crews are too nervous to come near due to the presence of foreign naval ships - including the USS Bainbridge destroyer.

FBI hostage negotiators became directly involved in the high-seas drama yesterday, but their efforts were met with defiance today when one of the pirates said the group would fight any attack by US naval forces.

“We are not afraid of the Americans,” one of the pirates told the Reuters news agency by satellite phone. “We will defend ourselves if attacked.”

Despite their defiant talk, maritime groups tracking the saga - the first time Somali pirates have captured an American - say a more likely outcome is a negotiated solution, possibly involving safe passage in exchange for their captive.

“Other pirates want to come and help their friends, but that would be like sentencing themselves to death,” said Andrew Mwangura, coordinator of the East African Seafarers’ Assistance Programme that monitors the region’s seas. “They will release the captain, I think, maybe today or tomorrow, but in exchange for something. Maybe some payment or compensation, and definitely free passage back home.”

Phillips is one of about 270 hostages being held at the moment by Somali pirates, who have been plying the busy sea-lanes of the Gulf of Aden and Indian Ocean for years. They are keeping 18 captured vessels at or near lairs on the Somali coast - five of them taken since the weekend alone.

General David Petraeus, the head of US Central Command, said last night that America would send reinforcements to the region within 48 hours.

“I would like to see it end peacefully and quickly,” the captain’s wife Andrea said in a TV interview. “If it’s money that they want, give them the money.”

More details have emerged about Wednesday’s dramatic seizure — and release — of the 509ft Maersk Alabama, which became the first US merchant vessel to be taken by pirates since the North African Barbary Wars two centuries ago.

The container ship was seized about 300 miles east of the Somali capital of Mogadishu as it carried food aid to Mombasa, Kenya. The ship was the sixth to be seized within a week; Somali pirates are ranging further afield to avoid the flotilla of international warships protecting the approaches to the Suez Canal.

Captain Joseph Murphy, a maritime instructor whose son is the ship’s chief mate, said that the container vessel was taken only after a chase that ended in heavy gunfire. “They outran the pirates for between three and five hours. They were finally overtaken. Substantial gunfire was involved,” he said.

Before the pirates used grappling irons to clamber aboard, the 20-man crew reportedly disabled the ship, as they were trained to do, to prevent the raiders sailing it into Somali territorial waters, where it is more difficult for foreign navies to operate.

All of the crew took refuge, except for Captain Phillips, one crew member said. “He stood by when everyone hid. He was the one the pirates got a hold of. He kind of surrendered himself to the pirates to protect the rest of the crew,” John White, an electrician aboard, told CBS News.

Shortly after they were boarded the unarmed crew managed to overpower one of the pirates even though they were carrying Kalashnikov rifles.

They locked themselves in the compartment that contains the ship’s steering gear, where they remained for about 12 hours with their captive. The three other pirates “got frustrated because they couldn’t find us”, Ken Quinn, the second mate, told CNN.

Mr Quinn said that the captain had talked the pirates into getting into the Alabama’s 28ft lifeboat and taking some money. Crew members agreed to exchange their captive pirate in exchange for Captain Phillips, Mr Quinn said, but the pirates reneged on their agreement.

“We returned him, but they didn’t return the captain,” Mr Quinn said. “Now they got our captain in the lifeboat. They got him hostage. They wanted an American captain to hold for ransom.”

There are emergency rations to last ten days on the lifeboat, but the conditions are most probably uncomfortable, according to Captain Murphy. “There’s no toilet facilities or anything like that,” he said.

Today the Maersk Alabama was heading for Mombasa with an 18-man US Navy guard aboard. The attack triggered an unexpected foreign policy crisis for President Obama, who refused yesterday to answer questions about the stand-off.

“This is being worked on around the clock,” Vice-President Joe Biden said. Officials said that all efforts were being made to ensure a peaceful outcome. Kevin Speers, a spokesman for Maersk, said: “The safe return of the captain is our foremost priority.”

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