The tribesmen have machine guns and swords
The tribesmen say they want to join the Taleban's "holy war" against the US.
But the Taleban's ambassador to Pakistan, Mullah Abdul Salam Zaeef, said there was "no need" for them at this stage.
"We have requested that since there are only air assaults in Afghanistan there is no need and great danger for them being there," he told a news conference in Pakistan.
"If they are needed then we will tell them," he said.
Slipping across
Pakistan officials say up to 9,000 tribesmen gathered at the border over the weekend.
Border guards have stopped them passing, although correspondents say the border is notoriously difficult to patrol and some may already have slipped across.
The Pakistan tribesmen gathered in response to calls for volunteers by local Islamic militants. Most come from villages inside the North West Frontier province, which has strong cultural and family ties with Afghanistan.
A reporter with the Associated Press who spent time with some of the men said they were armed with assault rifles, machine guns, rocket launchers, axes and swords.
The BBC's Susannah Price in Islamabad says the Pakistanis are concerned that, if any of the volunteers are killed, their funerals could become a rallying point for pro-Taleban supporters.
Pakistan's President Pervez Musharraf has been trying to stop popular protests at his government's backing for the US raids on Afghanistan from spiralling into wider unrest.
President Musharraf has repeated his concerns that the US-led raids should not continue into Ramadan, the Muslim month of fasting, which begins on or around 15 November.
"There is concern not only in the Islamic world, but the entire world, in the West and in the United States, at all the civilian casualties and the miseries that the civilians are being put through in Afghanistan," he said.
The US-led military campaign against the Taleban regime in Afghanistan began after it refused to hand over Islamic militant Osama Bin Laden, suspected of masterminding the 11 September terror attacks against New York and Washington.
Cleric's call
The call for volunteers was made by Sufi Mohammed, an outspoken Muslim cleric and head of Tehreek Nifaz-e-Sharia Mohammadi, a group which supports the imposition of Islamic Sharia law.
Our correspondent says that although the Taleban have many Arab, Pakistani and other foreign volunteers with them, they seem unenthusiastic about the prospect of untrained, foreign fighters joining them.
In a separate show of opposition to the US strikes, pro-Taleban Pakistanis were reported to still be blocking a key transport link between the country and China.
Reuters reported that up to 60 tribesmen were blocking the Karakoram Highway in the small mountain town of Besham, 200 kilometres (125 miles) north of Islamabad.
Riaz Durrani, a spokesman for Jamiat Ulema-e-Islam, an influential Pakistani religious party, said: "Tribesmen have closed it to express solidarity with Taleban and to participate in the agitation launched against government's support for America".
A disused airstrip was also reported to have been occupied at the remote town of Chilas in the disputed Northern Areas.