A delegation of Pakistani officials is reported to be in Afghanistan to deliver an ultimatum to the Taliban telling them to hand over Osama bin Laden or face military action.
A government spokesman said Pakistan was in contact with the Afghan government through diplomatic channels but refused to disclose what would be discussed when both parties meet.
However, CNNhas reported that Pakistan is to give the Taliban three days to hand over bin Laden.
The ultimatum comes after a late-night phone discussion between US President George W Bush and Pakistan's president Gen Pervez Musharraf.
Today President Musharraf met politicians and Islamic clerics to get their support for his promise to give "full support" to the US to retaliate for the attacks.
Islamic hardliners in Pakistan have demonstrated against the plans, burning US flags and shouting slogans in support of bin Laden and the Taliban.
They also warned the Pakistani government they would fight on the side of Afghanistan's Islamic militia.
"If Afghanistan is attacked we will take part in the fight against America," shouted militant Muslim leader, Abdul Ahad, to an estimated 1,000 demonstrators in northwest Pakistan, near the Afghan border.
In the capital of Islamabad, demonstrators chanted anti-American slogans.
AP &