"If America will not meet our demands we will kill Daniel," the unsigned message said. "Then this cycle will continue and no American journalist could enter Pakistan."

The message said that unless the kidnappers' demands are met, "the Amrikans (Americans) will get what they deserve."

The latest e-mail gave no reason why the deadline for Pearl's killing had been extended, and no time was given for the start of the countdown.

The Journal on Thursday had appealed to Pearl's captors, urging them to spare the journalist's life after the first death threat was made.

"Killing Danny will achieve nothing for you," Journal managing editor Paul Steiger said in an e-mail to the kidnappers Thursday. "His murder would be condemned by the entire world, and your group would be viewed as murderers without serious political objectives."

Steiger said the kidnappers should release Pearl with a "detailed list of the issues and grievances that are important to you" so that he "can articulate them to others."

"Only through Danny's safe release can your group have the opportunity to tell your side of the story and to have the entire world focus on your words," Steiger said.

There was no way to authenticate the e-mail death threats, which were sent to both Western and Pakistani news organizations.

Wednesday's e-mail claimed that Pearl, the Journal's South Asian bureau chief who disappeared a week ago in Karachi, was an agent for the Israeli intelligence service, the Mossad.

"Therefore we will execute him within 24 hours unless Amreeka [America] fulfills our demands," it warned.

The e-mail also accused United States journalists of working for intelligence agencies and said they should leave the country within three days, threatening "anyone remaining after that will be targeted."

The U.S. was also criticized for not providing lawyers and trials for Pakistanis detained on terrorism-related charges. The message was not signed, but contained wording similar to e-mails sent over the weekend by the previously-unknown group claiming to hold Pearl, the National Movement for the Restoration of Pakistani Sovereignty.

The group sent e-mails demanding that Pakistanis held by the U.S. military at Guantanamo Bay, Cuba, be returned here for trial.

Pearl's wife, Marianne, who is pregnant, said in an interview distributed to Pakistan TV and to all the American networks that she and her husband believed their role as journalists was to create dialogue.

She appealed to the kidnappers to open a dialogue with her about winning her husband's freedom.

"This is completely wrong, to hold us. It's just creating more misery and that's it. Nothing can come out of there," she said.

Asked if she had a message for her husband, Marianne Pearl said: "I love you."

She said the two typically worked on stories together.

"I'm pregnant, I was sick. Otherwise I would have gone with him," she said.

She said she had not slept in six days, but was not desperate and was keeping up hope.

In a statement Wednesday, the Journal denied that Pearl was an agent of any government. "He is a reporter for us — nothing more or less," the statement said. "He cannot affect the policy of the U.S. or Pakistani government. Nor can we."

Earlier Wednesday, police said they had arrested Sheik Mubarak Ali Shah Gilani, an Islamic leader with whom Pearl was trying to arrange an interview when he disappeared.

Gilani, head of the small militant group Tanzimul Fuqra, was apprehended in the northern city of Rawalpindi and transported to Karachi, police official Mazoor Mughal said.

There was still no word on where Pearl, 38, was being held by his captors, but police said raids were carried out Wednesday in several Pakistani cities in connection with the investigation.

Pakistani authorities said Pearl was most likely being held by a known radical Muslim faction linked to the Al Qaeda terrorist organization.

When trying to meet Gilani, Pearl was working on various stories, including possible links between Pakistani groups and Richard C. Reid, accused of trying to blow up an American Airlines plane with bombs hidden in his sneakers.

The weekend e-mails showed pictures of Pearl in chains with a pistol pointed at his head. It also included a list of demands, including better treatment for Pakistanis held with other terrorist suspects by U.S. authorities at Guantanamo Bay, Cuba.

Steiger previously sent a six-paragraph e-mail back to Pearl's captors, pleading for them to release him and mentioning the reporter's family.

"You should know that Danny has a wife," the e-mail by Steiger read. "She is a citizen of France, and also a journalist. She is also six months pregnant with their first child. I would like you to know that she is greatly distressed over Danny's situation."

"I encourage you to correspond with me further through this e-mail address," Steiger wrote in the message.

The State Department warned U.S. citizens Wednesday to consider carefully plans to travel to Pakistan. Unconfirmed reports that Americans have been targeted for kidnapping or other terrorist actions were cited by the department in a statement to the media and to U.S. diplomats. The warning cited Pearl's disappearance.

The Associated Press contributed to this report.