WASHINGTON -- U.S. authorities warned that terrorists could launch a fuel tanker attack on U.S. interests at home and abroad, notably Jewish targets, although officials reportedly were backing away Saturday from an earlier report that the city of Las Vegas was a prime target, AFP reported.

Federal Bureau of Investigation (FBI) agents have "received uncorroborated information that terrorists may be interested in using fuel tanker trucks for attacks against U.S. interests in the United States or overseas, notably against Jewish schools and synagogues," FBI spokesman Paul Bresson said.

Emphasizing that most of the information was uncorroborated or unconfirmed, another spokesman, Bill Carter, said the warning had nevertheless been passed on to law enforcement agencies "out of an abundance of caution." Despite the alleged threat, Jewish organizations urged congregations to attend their synagogues as usual on the Jewish Sabbath, which runs from sunset Friday to the same time Saturday.

"If synagogues are open, they should remain open," said Myrna Shinbaum, a spokeswoman for the Anti-Defamation League, a Jewish advocacy group.

She said the organization was advising synagogues to have members call 911 if they spotted fuel trucks approaching.

Earlier Friday the FBI had been weighing the seriousness of warnings that terrorists were planning an Independence Day attack on Las Vegas, Nevada, after a man said he intercepted a cell phone conversation in Arabic last week in which such an attack was discussed.

U.S. news media reported Friday that Lebanese-American Michael Hamdan, a resident of Las Vegas, reported overhearing a conversation in Arabic on his cell phone plotting the July 4 attack.

He told officials that an anonymous voice declared: "We are here in the city of corruption, the city of prostitution and gambling, the city of the unbelievers, and they are talking about freedom. We are going to hit them on the day of freedom." CNN reported however that officials had since determined that Hamdan was not credible, saying that he failed a lie detector test administered by authorities.

The report of a possibel Independence Day attack tapped into a deeply-held fear in the United States: More than half the U.S. public believe that a terrorist attack could occur on July 4th, according to a ***Time ***magazine/CNN poll released Friday.

Of 57 percent of people surveyed who believed an attack was a definite possibility, 13 percent said they thought an attack was very likely compared with 44 percent who said it would be somewhat likely, according to the poll.