KUWAIT CITY -- Americans, Britons and other Westerners filled planes flying out of Kuwait on Monday, responding to their governments' warnings and fears of chemical and terrorist attacks as a war with Iraq raced nearer.

On the Kuwaiti-Iraqi border, the United Nations all but abandoned the 120-mile frontier, leaving only a small group of Bangladeshi peacekeepers in armored vehicles between the U.S. and British armies and the Iraqi unknown.

"I think this time, it's going to happen," said Fred Skovberg, a Canadian who was among crowds of Westerners at Kuwait's international airport.

Several Western nations and Japan put out security warnings Monday for their diplomats and citizens in Mideast countries, ranging from embassy evacuations to recommendations of cautious behavior.

But while some foreigners are leaving, many others are not. Tens of thousands of Indians, Bangladeshis, Sri Lankans, Pakistanis and Filipinos who work in a variety of skilled or semiskilled jobs remain Kuwait.

U.S. and British diplomats called on their nationals in Kuwait to leave immediately -- warning that the airport and airspace could close to civilians if fighting starts.

"It's a good time now for people to take advantage of the fact that airspace is currently open to get out," U.S. Embassy spokesman John Moran said.

The British Embassy was talking to British Airways about laying on extra flights to speed the exodus of 3,000 to 3,500 Britons, Australians, Canadians and others.

So many Americans and Britons are leaving Saudia Arabia "it has become difficult to find a single vacant seat on most flights," said Said al-Moussa, a marketing manager at a travel agency in Riyadh.

Companies in Saudi Arabia have advised families of their foreign workers to leave the country, and schools near the Iraqi border in Tabuk, Araar and al-Qaryat will be closed by week's end. The Araar and Tabuk airports already are closed to civilian traffic.

Similar security has been enacted in eastern Saudi Arabia close to the Kuwaiti border, officials said. However, King Fahd international airport in Dammam in east-central Saudi Arabia is still operating.

In Egypt, a security official at Cairo airport, Lt. Mohammed Salamain, said passengers from other Arab states would be granted visas on arrival in the event of war.

"I think that Kuwait will be 98 percent safe -- but you never know what Saddam Hussein could do if he's backed into a corner," said Hope Brunn, 37, of Huntington, N.Y., who was leaving with her 8-month-old daughter, Zahra.

The U.S. and British governments warned of the risk of chemical or biological attack -- not just from Iraqi missiles, but from terrorists inside Kuwait.

Many of those leaving cited that risk. Some said war did not worry them as much as a backlash by Islamic militants.

"If this 'impenetrable defense' is broken, and a chemical weapon gets through and reaches me, my kids don't have a father for the rest of their lives," said Rick Rolls, a 44-year-old teacher from North Bay, Ontario.

Despite the unease, the U.S. Embassy said it expected only about 500 to 1,000 Americans to heed the warning.

Most of the rest of the roughly 9,000 Americans here are spouses or children of Kuwaiti nationals, contractors for the U.S. military or members of the nearly 1,000-strong journalist contingent covering the war, the embassy said.

Kuwait is the launch pad for any attack on Iraq, hosting the bulk of the nearly 300,000 troops massed in the Persian Gulf.

The State Department ordered all government dependents and nonessential staff out of Kuwait, as well as Syria, Israel, and the West Bank and Gaza, citing the "deteriorating security situation in the region."

On Monday, convoys of U.N. vehicles moved from the heavily fortified Kuwait-Iraq border as blue-capped U.N. monitors pulled out with their U.N. Bangladeshi guards. U.N. observers have been patrolling the 16-mile-wide demilitarized zone since shortly after the 1991 Gulf War.

Kuwait has sealed the border with electrified fences, mounds and ditches, trying to guard against Iraqi incursions.