Two Taiwanese businessmen have been charged with trying to smuggle U.S.-made weapons to Iran, the latest in a string of illegal arms sales foiled by law enforcement activities increased in the aftermath of Sept. 11.

Federal authorities announced Tuesday that a U.S. grand jury in Baltimore indicted En-Wei Eric Chang, a naturalized American living in Taiwan, and David Chu, a Taiwan resident, on charges they tried to buy early warning radar, Cobra attack helicopters and U.S. spy satellite photos for Iran in violation of U.S. embargoes against that country.

Chu was arrested during a sting operation in Guam, but Chang remains a fugitive, authorities said.

"The object of the conspiracy was to enrich the defendants by shipping aircraft, helicopter, and weapons system parts to Iran through Taiwan and elsewhere," the indictment said.

Officials said the indictment resulted from a yearlong arms-smuggling investigation that grew out of a new cooperative program created by U.S. officials after Sept. 11 that encourages American sellers of sensitive military equipment to report suspicious inquiries and sales.

Authorities said the men came to their attention after one contacted a Maryland company about buying satellite images of Tehran.

Federal agents set up a fictitious business in Maryland, which Chang contacted by e-mail and asked to buy the latest military night-vision equipment, military helicopters and helicopter parts and special antennae used by pilots to detect enemy radar, authorities alleged.

Authorities said they have foiled several other recent attempts by foreigners to smuggle U.S. military materiel, including parts for surface-to-air missiles, fighter jets and spymaster equipment, to locations including China, Pakistan and Iran.

In at least one of the cases, Americans have been charged not with knowingly selling military goods to potentially hostile countries but rather allowing themselves to be duped into such sales without regard for where the technology might eventually end up.

While the government long has sought to stop exports of such technologies to banned countries, officials say the recent spate of cases reflects a new approach and heightened awareness that enemies may try to use America's own weapons against it.

"What gives the United States military its edge? Our technology," said U.S. Attorney Thomas DiBiagio, who supervised the Baltimore case. "It's what we have and they want. ... Certain countries are willing to pay large amounts of money for it."

"There's a tremendous amount of money to be made by businessmen who can move what we might consider secondhand parts," he added.

The case was led by the new Bureau of Immigration and Customs Enforcement, the Homeland Security successor to the former Customs Service criminal investigations office. It has received numerous recent tips from U.S. companies under the program designed to prompt makers of sensitive technology to report suspicious inquiries and buys.

Called "Shield America," the initiative already has contacted more than 5,700 U.S. companies and sellers of weapons technology, and the list is growing. Recent investigations have yielded some dramatic results.

Last Thursday, federal prosecutors in Los Angeles announced grand juries had indicted four individuals and three companies with attempting to provide parts for Hawk surface-to-air missiles, TOW anti-tank missiles and Sidewinder air-to-air missiles to China.

The defendants also are accused of selling parts for F-4 Phantom jets and were nabbed as part of a five-year undercover investigation into weapons smuggling to China, officials said.

China and Iran, though not current targets of the war against terror, have emerged in several recent cases, some that began developing in the weeks before the Sept. 11, 2001, attacks.

In Milwaukee, three people and three companies were indicted for trying to export parts for F-4 and F-15 fighter jets and military helicopters destined for Iran, as part of an undercover government sting.

In that case, the government alleges most of the defendants didn't know the parts were meant for Iran but failed to find out where they were headed. "The indictments allege that these companies acted as if they did not care," U.S. Attorney Steven Biskupic said.

Last summer, a man was sentenced to prison in New York for a scheme to smuggle helicopter machine gun parts and other military equipment through Switzerland to Iran, officials said.

Authorities say Iran, which formerly bought military hardware from the United States before the 1979 Islamic revolution, holds many aging American-made fighter jets and missiles systems. It consistently tries to buy U.S. parts secretly to keep the old materiel operational.

And last October, two people in Baltimore were sentenced to prison for conspiring to export to China through Singapore sensitive encryption technology designed to keep material secret even from spymasters.