US reviewing passport controls

Concerned about a potential terrorist attack, US authorities are reviewing systems used to screen airplane passengers with Western passports before they board flights to the United States.

Officials are assessing checks and safeguards at airports "to ensure that they are adequate", Homeland Security Secretary Jeh Johnson said at the Council on Foreign Relations on Wednesday.

Since the Syrian civil war erupted in 2011, more than 4,000 foreign fighters have travelled there, including about 1,000 people with European or other passports that normally assure easy entry to the US, Johnson said.

In addition, more than 100 Americans have travelled or tried to travel to Syria to join rebel groups fighting against Bashar Assad's government.

US officials are especially concerned that fighters from England, France, Germany or 35 other countries whose citizens can visit the US without a visa will try to blow up a jetliner bound for the US or launch an attack inside the country.

Under current rules, passengers from so-called visa waiver countries must complete an information form 72 hours before they depart.

But not all the forms are checked for accuracy and some security officials would like more details collected before a flight.

Johnson said his department had enhanced aviation security overseas in the past three months after evidence suggested militant groups based in Syria and Iraq could target US-bound aircraft.

Since July, the US has boosted security screening of passengers and carry-on luggage in 25 foreign airports with direct flights to the US, he said.

"We need to ensure we are doing all we can to identify those who, by their travel patterns, attempt to hide their association with terrorist groups," Johnson said.

President Barack Obama will lead a UN Security Council meeting on September 24 during the annual General Assembly session in New York. It is rare for a sitting US president to attend Security Council proceedings.

Obama is expected to seek a UN resolution requiring countries to collect and share more information about the travel of foreign fighters and other potential terrorists.