Citing a crisis of "stunning proportions," the U.N.'s top relief agencies joined together Tuesday in a desperate plea for countries around Afghanistan to re-open their sealed borders and accept thousands of refugees.

The U.N. High Commissioner for Refugees and several other groups said they would visit sites along the Pakistani-Afghan frontier over the next few days to identify border crossing and refugee camps that can be re-opened to "what could become a flood of men, women and children," according to one official.

But the officials could offer no guarantee that fighters for the Taliban government, Usama bin Laden or other terrorist groups or militias would not be among those crossing the border, presumably to seek shelter from what is expected to be a sharp American response to the Sept. 11 terrorist hijackings.

Officials with the U.S. and other Western countries concede the humanitarian situation in Afghanistan has been desperate for some time — well before the threat of a U.S. military strike became a reality. More than 5 million Afghans currently require humanitarian assistance to survive and thousands of children are said to be near starvation.

Several countries, however, chief among them Pakistan, worry about the security issues of letting even larger numbers of Afghans into their country. Pakistan already hosts some 2 million Afghan refugees, and could receive hundreds of thousands more in the aftermath of a U.S. military strike. Tens of thousands of refugees are already on the move in anticipation of an American attack.

U.N. officials said the job of identifying potential terrorists and Afghan combatants among the refugees was the job of the host countries, and not of the various international agencies that have offered their help in delivering food and other supplies to the region.

"They have not posed a threat to any country, in the vast majority of cases, that we're aware of," UNHCR told reporters at a jammed early evening news conference. "We don't believe they are a danger. In societies where they've been integrated, they've been integrated well."

UNHCR spokesman Peter Kessler also said Afghan fighters, both those affiliated with the governing Taliban forces and anyone else, would be considered legitimate refugees if they simply laid down their weapons and fled the country in the wake of an American attack.

"Anyone who puts down a weapon can be considered a refugee," Kessler said. "It’s up to the country, the Pakistan government in this case, to monitor the situation."

That policy might put the UNHCR somewhat at odds with the Bush administration, which has vowed to track down those who were in any way responsible for or sheltered those involved in the Sept. 11 attacks.

Bush has repeatedly said he plans a long and sustained campaign against those responsible for the attacks, so it's not clear how he would address the issue of terrorists or terrorist supporters in the refugee camps.

Others said they feared the refugee camps could become prime recruiting grounds for anti-Pakistani or anti-Western sentiment. The camps often offer only the barest of necessities, and resentment and bitterness are not uncommon. Some refugees have lived in tent cities along the Pakistani-Afghan border for years, a situation that continues to worry Pakistan.

The international aid community has struggled with this issue in the past.

Palestinian refugee camps in Jordan and Lebanon, for example, became strong support bases for some of the area's more radical extremist groups in the 1970s and 1980s. And refugees in the camps set up in Albania during the Kosovo crisis in 1999 actually held parades and rallies for the Kosovo Liberation Army in the camps, to the surprise and dismay of the aid agencies. 

Nonetheless, U.N. officials believe the risk of terrorists slipping through the various security systems set up to catch them at border crossings and camps is worth saving what could be thousands of lives.

"In most cases, the government knows who they are looking for and can act appropriately," one aid worker said privately. "But if you’re asking if they could use more help, of course they could. We all could."