The 10-day extension came after leaders of the militia met Tuesday with one of the five fugitives, Naik Mohammed, at an undisclosed location in South Waziristan province, which borders Afghanistan.
Mohammed asked to be allowed to consult with his supporters until Friday before responding to demands from fellow Zalikhel tribesmen to surrender.
The May 1 deadline was announced in Peshawar, the capital of the northwestern border province, after a meeting between the governor, Syed Iftikhar Shah, and military leaders, officials said.
It came a day after a previous government deadline of April 20 for tribes to hand in people harboring terrorists or face a military crackdown.
Before announcing the new deadline, Shah met dozens of tribal elders, who asked for more time to hunt the fugitives. He said the government would extend the ultimatum but wanted results, according to Malik Waris Khan Afridi, who attended the meeting.
Tribal leaders pledged their help, fearing another crackdown by the army.
The extension of the deadline may reflect the delicate task facing the Pakistani government, which is trying to assert authority in a region normally beyond its control without provoking hard-liners who oppose Islamabad's cooperation with the United States.
Last month, more than 120 people were killed in a government operation against al Qaeda holdouts and allied tribesmen in the region. More than 160 militants were arrested, but no senior al Qaeda figures were among them, and hundreds of other suspects escaped.
The region is believed to be a hideout for foreign fugitives and Taliban fighters, including al Qaeda leader Osama bin Laden and his No. 2, Ayman al-Zawahri.
Meanwhile, Zalikhel tribe members began to reopen their shops in Wana, the main town in South Waziristan, after authorities lifted a ban aimed at pressuring the tribe to surrender the fugitives.
Pakistan's government, which has enraged religious hard-liners with its support of America's war on terrorism since the Sept. 11, 2001, attacks, has repeatedly ruled out such a move. President Pervez Musharraf was the target of two assassination attempts in recent months.
U.S. Ambassador to Afghanistan Zalmay Khalilzad last week twice criticized Pakistan for failing to stop cross-border infiltration by al Qaeda and Taliban rebels into Afghanistan.
Khalilzad said Pakistan continues to provide "a sanctuary" for al Qaeda and the Taliban.
"We all want Pakistan to deal with the problem," he was quoted as saying in Pakistani media. "The problem has not been solved and needs to be solved, the sooner the better."
Khalilzad also said the American military — which leads more than 13,000 troops hunting al Qaeda and Taliban holdouts in Afghanistan — would move forces into Pakistan if it failed to oust the terrorists.
Pakistan Foreign Ministry spokesman Masood Khan on Monday issued a stinging rebuke against the American envoy.
Khan said that "Pakistan is doing more than enough" to check activities of terrorists, and said Islamabad would protest the ambassador's comments to Washington.
"It is strange that he (Khalilzad) is working hard to create misunderstanding between the United States and Pakistan. He is new to the job and diplomacy but while in Afghanistan is not expected to make statements that impinge on Pakistan-U.S. relations," Khan said.