The world continued to wait for correspondence from the Pakistani group claiming to hold kidnapped Wall Street Journal reporter Daniel Pearl early Saturday as the extended Friday deadline for his execution seemed to pass without new information as to his location or condition.

Police in Karachi have searched 300 vacant lots and graveyards to see if the kidnappers carried out their threat to execute the journalist, but have found nothing.

On Friday, there were unconfirmed reports from senior Pakistani police officials that a caller purporting to represent the kidnappers telephoned the U.S. Consulate in Karachi and demanded $2 million and the release of the former Taliban ambassador to Pakistan.

The Pakistani officials, who spoke on condition of anonymity, said the caller gave the Americans 36 hours to meet the demand for money and the freeing of the envoy, Mullah Abdul Salaam Zaeef, who was arrested in Pakistan and handed over to U.S. authorities.

The officials said police believe the call may be genuine. A demand for Zaaef's release also was made in an e-mail sent Sunday by those claiming to hold Pearl.

But officials at the State Department in Washington and at the U.S. Embassy in Islamabad said they could not confirm that a phone call had been received.

President Bush said earlier Friday his administration will "chase down any leads" that may lead to Pearl's rescue, including e-mails purportedly sent by his captors.

"We are working with the Pakistan government to chase down any leads possible — for example, trying to follow the trail of the e-mails that have been sent, with the sole purpose of saving this man, of finding him and rescuing" him, Bush said during an Oval Office appearance with Jordan King Abdullah II.

"WE GIVE U 1 MORE DAY IF AMERICA WILL NOT MEET OUR DEMANDS WE WILL KILL DANIEL. THEN THIS CYCLE WILL CONTINUE AND NO AMERICAN JOUNALIST COULD ENTER PAKISTAN," said an e-mail, sent Thursday to Fox News, CNN, the BBC and three Pakistani newspapers. 

The e-mail, signed with the obvious pseudonym "Mujahid Islam," went on to say that "WE HAD GIVEN OUR DEMANDS AND IF U WILL NOT THEN "WE" WILL ACT AND THE AMRIKANS WILL GET TEIR PART WHAT THEY DESERVE." 

"DON'T THINK THIS WILL BE THE END," it continued. "IT IS THE BEGGINING AND IT IS A REAL WAR ON AMRIKANS.AMRIKANS WILL GET THE TASTE OF DEATH AND DESTRUCTIONS WHAT WE HAD GOT IN AFG AND PAK." 

"INSHALLAH," it concluded, using the Arabic for "God willing." 

A co-worker of Pearl's, Elaine Cooper, told Fox News' Rita Cosby that "letting him [Pearl] go would give these people the perfect opportunity … to represent their case."

"Harming Danny is only going to turn public opinion against them," she said.

Secretary of State Colin Powell said in Washington that "we are doing everything we can" to secure Pearl's safe release, but he ruled out meeting demands made in previous e-mails that Pakistanis held by the U.S. military in Guantanamo Bay, Cuba, be repatriated. 

Powell added that he had spoken with Pakistani President Gen. Pervez Musharraf, "and I know that he is doing everything he can." 

But he said "the demands that the kidnappers have placed are not demands that we can either deal with or get into a negotiation about." He insisted the detainees at Guantanamo "are being treated humanely" and "in accordance with international law." 

Meanwhile, Reuters reported Friday that Pakistani Foreign Minister Abdul Sattar said he had mobile phone records showing the chief suspect in the kidnapping had been in contact with three important Indian government officials.

It was impossible to be certain that Thursday's e-mail was actually sent by those who seized Pearl, 38, who vanished on Jan. 23 in Karachi. But anonymous Pakistani police sources said it appeared genuine. 

The first e-mail concerning Pearl, which was signed by a previously unknown group calling itself the National Movement for the Restoration of Pakistani Sovereignty, was sent Sunday and demanded that Pakistanis captured in Afghanistan and now held at Guantanamo be sent back to Pakistan for trial before Pearl could be released. 

It added that Pearl would be held in the same "inhuman" conditions as the Guantanamo prisoners, and attached several photographs of him, one of them showing him chained and with a pistol to his head, for verification. 

A second e-mail, sent Wednesday, set a 24-hour deadline before Pearl would be killed, and also accused him of working for the Israeli intelligence agency, the Mossad. It also demanded that all American journalists leave Pakistan within three days or become targets, and attached more photographs of Pearl. 

On Thursday, the Journal's managing editor, Paul Steiger, responded to the latest e-mail, urging the kidnappers to let Pearl go. 

"The world now knows, and you seem to know, that Danny is a journalist, nothing more or less," Steiger wrote. "Journalists are, by definition, trained messengers. Danny can be your messenger. A freed Danny can explain your cause, and your beliefs, to the world.... A captive or killed Danny cannot speak for you, cannot help you or your cause." 

Pearl's French-born wife, Mariane, who is several months pregnant, appealed to the kidnappers in a widely-distributed television interview 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, Mariane Pearl smiled and said: "I love you." 

American boxing legend Muhammad Ali, a Muslim, invoked Allah and asked Pearl's captors to show "compassion and kindness" and release him. 

"I have not lost Allah's hope in us to show compassion where none exists and to extend mercy in the most difficult of circumstances. We as Muslims must lead by example," the 60-year-old former heavyweight champion said in a statement. 

Reporters Without Borders, a non-governmental organization that promotes press freedom, urged five international Islamic religious figures to appeal for Pearl's release. The appeal was made in a letter to King Mohammed IV of Morocco and religious leaders in Egypt, Pakistan, Saudi Arabia and Qatar. 

Pakistani police claimed they were pursuing several leads but refused to give details. On Thursday, a source close to the investigation, speaking on condition of anonymity, said a key suspect known only as Arif was reported dead in southern Punjab province. 

The source said police went to Arif's home but was told by his family that he had died a few days ago in Afghanistan. Arif was believed to have been one of Pearl's contacts, the source said. 

On Wednesday, Pakistani 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. 

When trying to meet Gilani, Pearl, head of the Journal's South Asia bureau and based in Bombay, 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. 

Pakistani authorities think Pearl is most likely being held by a well-known radical Muslim faction — the Harkat ul-Mujahedeen, or Movement of the Holy Warriors — which has strong links to Usama bin Laden's Al Qaeda terrorist organization. 

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.