ISLAMABAD, Pakistan -- With Osama bin Laden exhorting followers to stay "steadfast on the path of jihad" - holy war - the hard-line Taliban government warned Monday the Americans they were "igniting a fire that will burn them" if they attack Afghanistan.
In signs of an intensifying showdown over Afghanistan's refusal to surrender bin Laden, the prime suspect in the devastating terror attacks on the United States, the Taliban drastically curtailed the activities of the remaining United Nations relief workers inside Afghanistan, and neighboring Pakistan pulled its diplomats out of the Afghan capital, Kabul, in what could be a prelude to severing diplomatic ties.
The Taliban, who control more than 90 percent of Afghan territory, have been battling a northern-based opposition alliance for control of strategic areas north of Kabul. Heavy exchanges of mortar and artillery fire could be heard Monday in the Panjshir Valley, 45 miles north of the Afghan capital.
The United States and its allies have increased contacts with those forces in preparation for a possible assault on both bin Laden's bases and his Taliban hosts.
Bin Laden's latest call to arms came in a statement provided Monday to Qatar's Al-Jazeera satellite channel, which the exiled Saudi multimillionaire and accused terrorist mastermind often uses to communicate with the outside world.
"I announce to you, our beloved brothers, that we are steadfast on the path of jihad with the heroic, faithful Afghan people," said the statement, signed by bin Laden and dated Sunday.
Bin Laden called on "our Muslim brothers in Pakistan" to do their utmost "to push the American crusader forces from invading Pakistan and Afghanistan."
The Taliban have rebuffed U.S. demands to hand over bin Laden in the wake of Sept. 11 suicide strikes that toppled the twin towers of the World Trade Center and wrecked one wing of the Pentagon. The Taliban have said they do not know where he is - a claim ridiculed by American officials - and that they were trying to pass on a request that he leave the country.
Bin Laden has twice denied involvement in the terror attacks. The United States has said it will produce evidence implicating him.
In several separate statements Monday, the Taliban adopted a bellicose tone. The defense minister said Taliban fighters have all the weapons and ammunition they need to fight off a U.S. ground or air assault, and that volunteers were swelling militia ranks.
"Around 300,000 experienced mujahedeen (holy warriors) are guarding the borders and all other important places in Afghanistan," said the minister, Mullah Obaidullah Akhund. He instructed the Afghan people to "remain vigilant and prepare for jihad" - holy war.
The Taliban's leader, Mullah Mohammed Omar, said killing bin Laden would not protect America against terrorism.
In a statement faxed to news agencies from his headquarters in Kandahar, Afghanistan, Mullah Omar called on the United States to withdraw troops from the Persian Gulf, eliminate its "bias" against the Palestinians and refrain from interfering in the internal affairs of Islamic countries.
"America wants to eliminate Islam, and they are spreading lawlessness to install a pro-American government in Afghanistan," Mullah Omar said. "This effort will not solve the problem, and the Americans are igniting a fire that will burn them if they indulge in this kind of activity."
Separately, the Taliban warned its northern neighbor, Uzbekistan, against aiding any U.S.-led coalition that moves against Afghanistan, saying that in the past, "imperialist forces" invading the country had met with defeat.
In Islamabad, however, the Taliban ambassador, Abdul Salam Zaeef, struck a somewhat more conciliatory note, recalling U.S. support to Islamic fighters during the Cold War battle with Soviet troops for control of Afghanistan. Zaeef said that assistance was still remembered and appreciated by the Afghan people.
But, he added: "We want to say once again that the people of America should urge their government to realize the grave consequences of war."
International agencies have been warning of a burgeoning humanitarian crisis inside Afghanistan, with civilians suffering from hunger and displacement. On Monday, a U.N. spokeswoman in Islamabad, Stephanie Bunker, said Taliban militia had begun entering U.N. offices in Afghanistan and threatening to kill workers unless they stopped using their communications and transportation equipment.
The move sharply reduced the relief work being done by Afghan staffers who were left behind when all foreign U.N. workers were withdrawn from Afghanistan recently.
"The U.N. has ordered its staff to obey the Taliban directive to avoid risking their lives," Bunker said. "This will have a very serious impact on our operations."
With Pakistan's withdrawal of its dozen diplomats from Afghanistan, the Taliban's diplomatic isolation grew. The United Arab Emirates severed diplomatic links over the weekend, leaving Afghanistan with formal ties only to Pakistan and Saudi Arabia.
"In view of the abnormal situation, they were withdrawn over the weekend, said Foreign Ministry spokesman Mohammed Riaz Khan.
Pakistan has agreed to support the expected U.S. military campaign against bin Laden and his Taliban allies, and the removal of diplomats appeared to reflect concerns over their safety if the United States launches airstrikes.