AMMAN, Jordan -- White police vans with bars on the windows cruise almost daily through Amman's industrial zone, where factories churn out everything from detergent to candy.

The first Iraqi worker to spot a police patrol rings a makeshift alarm, and others scatter to avoid getting caught working without valid residency permits.

"Everyone here is so afraid," said a 35-year-old secretary, who refused to be identified because she is here illegally herself. "If they get caught, they will be sent back to Baghdad for sure."

Fearing war with the United States, more Iraqis are trying to flee to neighboring Jordan. But the reception in Jordan, never warm, has become markedly less friendly, according to displaced Iraqis, aid workers and U.N. officials.

Border controls are being tightened and residency permits shortened, they say; raids and identity checks in factories and Iraqi neighborhoods are being stepped up; and people here illegally -- especially military-aged men -- are being deported, they say.

Government officials say they are simply enforcing rules to crack down on illegal workers in Jordan, where the unofficial jobless rate reaches 25 percent.

Yet the focus is clearly on Iraqis, observers say.

"In the current situation, the government is obviously on its toes," said Sten Bronee, the U.N. refugee agency representative in Jordan.

"There are indications that people are not being allowed into Jordan like they used to be. Increasing numbers of Iraqis are being detained pending deportation."

Although Iraq recently canceled the departure tax that prevented many from leaving, it is not allowing men of military age to go, said Jamal Hattar, director of the Caritas aid group in Jordan.

In addition, young men caught in Jordan illegally are reportedly being sent directly back to Iraq now instead of being given the option to go somewhere else where a visa is not required, such as Yemen, he said.

"Being a next-door neighbor, it's a very sensitive issue to accept asylum seekers here," Hattar said. "This would imply that you are working against Iraq."

Jordan, a key U.S. ally in the region, strives also to stay on good terms with Iraq, which provides it with free or discounted oil and buys more of its exports than any other single country.

Moreover, Jordan is afraid of being overwhelmed by a new tide of Iraqis, on top of the estimated 350,000 who have arrived since the 1990-91 Gulf War and stayed, most of them illegally.

More than half the desert kingdom's 5.2 million people already are or were refugees -- Palestinians displaced by the 1948 and 1967 Arab-Israeli wars.

"It's quite delicate here, the balance, the ethnic social fabric," said Saif Ibrahim, an economist at the Center for Strategic Studies at the University of Jordan. "They don't want to create a humanitarian catastrophe, but they don't want to be trapped politically with the issue of Iraqi refugees."

If a new conflict breaks out, King Abdullah II insists Jordan will allow in only refugees en route to a third country. His newly launched "Jordan First" national advertising campaign is seen partly as an attempt to head off public demands to do more if the situation worsens.

A former government official, who spoke on condition of anonymity, said Jordan had to preserve its own interests as a small country that has seen repeated waves of refugees from the Palestinian territories, Lebanon and Iraq.

"Nobody ever goes home," he added.

Yet despite the new difficulties, the flow doesn't seem to be stopping.

"There are a lot leaving (Iraq) now because of the threat of war," said Dr. Angie Schupp, an American who helps run a clinic for Iraqi refugees in Amman. "They don't want to be there if America strikes."