A 20-year-old Saudi student has been arrested in Texas in a bomb plot that may have targeted former President George W. Bush, nuclear plants and dams, U.S. authorities said on Thursday.

Khalid Aldawsari, who was admitted to the United States in 2008 on a student visa and was attending college in Lubbock, Texas, was arrested on Wednesday by FBI agents, the U.S. justice department said.

The arrest, tied to a threat that authorities described as "imminent," underscored growing concerns by U.S. officials that a person acting alone might carry out attacks inside the United States. They described the suspect as acting on his own and not part of an extremist group.

"The arrest once again underscores the necessity of remaining vigilant against terrorism here and abroad," White House spokesman Jay Carney said. President Barack Obama was briefed about the case earlier this month and was alerted on Wednesday evening about the imminent arrest, he said.

Aldawsari was arrested on terrorism charges involving the purchase of chemicals and equipment to make a bomb, with potential targets that included nuclear power plants and hydroelectric dams in the western United States, according to court documents.

One of his e-mails included Bush's Dallas address. Another cited three former U.S. military members who had been stationed at the Abu Ghraib prison, where Iraqis faced abuses by their American jailers, an FBI agent said.

The agent said in a written affidavit that Aldawsari also may have considered targeting a Dallas nightclub with explosives in a backpack, using a baby doll to conceal explosives, and putting bombs in rental cars in New York City.

U.S. officials said Aldawsari described his desire for violent jihad and martyrdom in blog postings and in a personal journal that listed tasks to perform such as getting fake U.S. documents and renting cars to hide bombs in them in New York.

Aldawsari also sent himself an e-mail titled "Tyrant's House," in which he listed the Dallas address for Bush, who moved there after leaving the White House in early 2009, authorities said.

A Bush aide declined comment. Apart from publishing his memoirs, the former president has largely stayed out of the limelight, but remains a focus of anger for some anti-American militants for the U.S.-backed wars in Iraq and Afghanistan.

The FBI received a report on Feb. 1 from a chemical supplier about an attempt by Aldawsari to buy concentrated phenol, which can be used to make an explosive.

The shipment was sent to a freight company but the firm returned it to the supplier and called the police, the Justice Department said. Aldawsari told the supplier he was connected to a university and was doing "off-campus, personal research."

SUSPECT FACES UP TO LIFE IN PRISON

If convicted, Aldawsari faces up to life in prison. He is due to make an initial appearance in court on Friday in Texas.

U.S. officials said Aldawsari had been researching online how to build a bomb using several chemicals as ingredients, and acquired most of the ingredients and the necessary equipment, an FBI agent said in a court affidavit.

In December and January, he purchased concentrated nitric and sulfuric acids, a gas mask, a Hazmat suit, a soldering iron kit, glass beakers and flasks, wiring, a stun gun, clocks and a battery tester, according to the affidavit.

The FBI also noted he had bought Christmas lights and that the wires in them could be used in building a bomb.

Aldawsari also e-mailed himself instructions on how to convert a cell phone into a remote detonator and how to prepare a booby-trapped vehicle using items available in every home, according to the FBI.

One of his e-mails contained a message stating that "one operation in the land of the infidels is equal to ten operations against occupying forces in the land of the Muslims," according to the affidavit.

FBI agents in an authorized search of Aldawsari's apartment this month found a notebook that appeared to be a diary or journal, the agency said.

According to the affidavit, excerpts from the journal indicated he had been planning to commit a terrorist attack in the United States for years.

It quoted one of his entries as saying, "And now, after mastering the English language, learning how to build explosives and continuous planning to target the infidel Americans, it is time for Jihad."

The affidavit cited another entry in which Aldawsari said the events on Sept. 11, 2001, produced a big change in his thinking and that speeches by al Qaeda leader Osama bin Laden inspired him.