The pirates tried to hijack the U.S.-flagged Maersk Alabama on Wednesday, but Capt. Richard Phillips thwarted their takeover by telling his crew of about 20 to lock themselves in a room, the crew told stateside relatives.

The crew later overpowered some of the pirates, but Phillips surrendered himself to the bandits to safeguard his crew, and at least four of them fled with him to an enclosed lifeboat, the relatives said. It was the first such attack on American sailors in about 200 years.

Kevin Speers, a spokesman for the Maersk shipping company, said the pirates have made no demands yet to the company and the captain's safe return is its top priority.

The Maersk Alabama is again sailing toward the Kenyan port of Mombasa — its original destination, according to Capt. Joseph Murphy, a professor at the Massachusetts Maritime Academy whose son, Shane Murphy, is second in command. A person reached by The Associated Press by phone on the bridge of the vessel confirmed: "We're moving."

A U.S. official, speaking on grounds of anonymity because of the sensitivity of the situation, also said a military team of armed guards was aboard the Maersk Alabama. Joseph Murphy said there were 18 guards aboard.

Earlier Thursday, the USS Bainbridge arrived near the Maersk Alabama and the lifeboat with the pirates and Phillips, Speers told AP Radio, adding that the lifeboat was out of fuel and "dead in the water."

The U.S. Navy sent up P-3 Orion surveillance aircraft and had video of the scene.

More U.S. ships will be in the area within 48 hours, said Gen. David Petraeus, head of the U.S. Central Command. He did not give specifics, but said "we want to ensure that we have all the capability that might be needed over the course of the coming days."

The lifeboats usually are about 28 feet long, designed to hold a maximum of 34 people, and made of reinforced Fiberglas, Joseph Murphy said. They carry water and food for 34 people for 10 days and with portholes closed, no one can see inside, he added.

President Barack Obama, facing one of his first national security tests, declined to comment on the standoff. Attorney General Eric Holder said the FBI was assisting the Navy.

"We're in contact with the people on the scene off the coast of Africa," he said. "The FBI people are here at Quantico and so they are using telecommunications means to stay in touch with them."

FBI spokesman Richard Kolko described the bureau's hostage negotiating team as "fully engaged" with the military on ways to retrieve Phillips.

One senior Pentagon official, speaking on grounds of anonymity because of the sensitivity of the situation, described it now as a "somewhat of a standoff."

Though officials declined to say how close the Bainbridge is to the pirates, one official said of the bandits: "They can see it with their eyes." He spoke on condition of anonymity due to the sensitivity of talking about a military operation in progress.

The Bainbridge was among several U.S. ships that had been patrolling in the region when the 17,000-ton Maersk Alabama was attacked. It was the sixth vessel to be hit by pirates in a week.

After the pirates came aboard the Maersk Alabama, Phillips told the rest of his crew by radio to lock themselves away in a room, according to the wife of Ken Quinn, a second mate on the vessel.

"He said the pirates were desperate," said Zoya Quinn of Bradenton, Florida, who spoke to her husband via phone and e-mail. "They were going all over the stairs, back and forth, trying to find them and they couldn't find them."

Quinn and the crew held one of the pirates for about 12 hours before releasing him in hopes of winning Phillips' freedom, she said, adding that the crew communicated with the bandits with hand signals until they left with the captain.

Quinn said he dressed an injured pirate's cuts with bandages "because he was bleeding all over the ship," she said, adding it was unclear how he was hurt.

The Maersk Alabama is expected to arrive in Kenya on Saturday, said Murphy, who spoke to the shipping company.

"From the standpoint of the families, we're ecstatic," he said. "The families, the crew themselves have been under a lot of stress."

Somali Foreign Minister Mohamed Omaar told the AP that the pirates "have got themselves into a situation where they have to extricate themselves because there is no way they can win."

Phillips' family was at his Vermont farmhouse, anxiously watching news reports and taking telephone calls from the State Department.

"We are on pins and needles," said Gina Coggio, 29, half sister of Phillips' wife, Andrea. "I know the crew has been in touch with their own family members, and we're hoping we'll hear from Richard soon."

Phillips surrendered himself to the pirates to keep the crew safe, Coggio said.

"What I understand is that he offered himself as the hostage," she said. "That is what he would do. It's just who he is and his response as a captain."

Steve Romano, a retired head of the FBI hostage negotiation team, said he doesn't recall the FBI ever negotiating with pirates before, but he said this situation is similar to other standoffs. The difficulty will be negotiating with people who clearly have no way out, he said.

"There's always a potential for tragedy here, and when people feel their options are limited, they sometimes react in more unpredictable and violent ways," Romano said.

The question now, he said, is: "How much do they value their own lives? Because their only motivation now is to try to survive this incident."

With one warship nearby and more on the way, piracy expert Roger Middleton of the London-based think tank Chatham House said the pirates were in "a very, very tight corner."

"They've got only one guy, they've got nowhere to hide him, they've got no way to defend themselves effectively against the military who are on the way and they are hundreds of miles from Somalia," he said.

Other analysts say the U.S. will be reluctant to use force as long as one of its citizens remains hostage. French commandos, for example, have mounted two military operations against pirates once the ransom had been paid and its citizens were safe.

Many of the pirates have shifted their operations down the Somali coast from the Gulf of Aden to escape naval warship patrols, which had some success in preventing attacks last year.

Ship owners often do not arm their crews, mainly because of the cargo. A Saudi supertanker hijacked last year was loaded with 2 million barrels of oil. The vapor from that cargo was highly flammable; a spark from firing a gun could cause an explosion.

There is also the problem of keeping the pirates off the ships — once they're on board, they will very likely fight back and people will die.

Pirates travel in open skiffs with outboard engines, working with larger ships that tow them far out to sea. They use satellite navigational and communications equipment, and have an intimate knowledge of local waters, clambering aboard commercial vessels with ladders and grappling hooks.

Any blip on a ship's radar screens is likely to be mistaken for fishing trawlers or any number of smaller, non-threatening ships that take to sea every day.

It helps that the pirates' prey are usually massive, slow-moving ships. By the time anyone notices, pirates will have grappled their way onto the ship, brandishing AK-47s.