(CBS News) PENTAGON - Secretary of Defense Chuc

(CBS News) PENTAGON - Secretary of Defense Chuck Hagel said Tuesday that U.S. military forces are ready to go if and when the president gives the green light for a strike against Syria.

U.S. military action would be punishment for the chemical weapons attack last week that left more than 300 Syrian civilians dead, many of them women and children.

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Vice President Joe Biden became the highest-ranking administration official to declare the Assad regime was behind that attack, although the Syrian government denies it .

Vice President Joe Biden

/ AP Photo/Manuel Balce Ceneta

U.N. inspectors have not finished their investigation, but U.S. officials say they have their own intelligence.

Before the U.S. acts, it plans to publicly reveal some of the intelligence which Biden said Tuesday proves who is to blame for the mass casualties in Syria.

"There is no doubt who is responsible for this heinous use of chemical weapons in Syria: The Syrian regime," he said.

The intelligence -- much of it still classified -- ranges from intercepted Syrian communications to tests of tissue samples taken from victims, down to the simple fact that the regime is the only one in Syria known to have chemical weapons. But British Prime Minister David Cameron warned there is no smoking gun.

"There is never 100 percent certainty," he said. "There is never one piece or several pieces of intelligence that can give you absolute certainty."

The U.S. has moved four destroyers, like the one above, into the eastern Mediterranean if and when the president orders an attack on Syria.

/ CBS News/Dept. of Defense

Traveling in Asia, Hagel spoke by phone with the defense ministers of Britain and France, two countries which have pledged to join the U.S. in punishing Syria for using chemical weapons. Then, he was asked by a BBC reporter if the Pentagon, which has moved four destroyers into the eastern Mediterranean, is ready to strike.

"If the order comes, you're ready to go, like that?" the reporter said, snapping his fingers.

Secretary of Defense Chuck Hagel speaks on the phone with his counterparts in Britain in France Tuesday, August 27, 2013, about a potential attack on Syria.

/ syria,department of defense, hagel

"We are ready to go like that," Hagel responded .

Each of the destroyers carries about 40 cruise missiles, a satellite-guided weapon that carries a 1,000-pound warhead, has a range of 1000 miles or more and an accuracy to within about 15 feet.

Standard procedure would be for the ships to fire an opening salvo at night, wait for satellites to assess the damage and re-strike any targets that were not destroyed -- a process that could take a few days.

The British parliament will meet in emergency session on Thursday to vote on a motion authorizing military action. Although President Obama has not yet made a final decision, U.S. officials expect the strike to begin soon after that.

In response to an attack, Syrians could try to attack the fleet of ships, but the ships are probably to off shore and too well-defended for that to be successful. They could also try and use chemical weapons again, since it is unlikely a single strike will completely eliminate their supply.