MONTREAL - A top official with the International Civil Aviation Organization says he expects airline passengers to be able to bring gels and liquids back on board within a couple of years.

Secretary general Raymond Benjamin says a group of ICAO experts has been looking into technology which he hopes, will allow liquid explosives to be detected at the operational level of airports -- within two years.

He says once the technology is in place, passengers will again be allowed to bring their liquids and gels on planes.

But that was news to U.S. Homeland Security Secretary Janet Napolitano who said Tuesday it's too early to say when aviation officials can lift a ban on liquids on board flights.

Benjamin told reporters on Tuesday at the start of ICAO's 37th assembly the new technology will also mean additional costs, which, at the end of the day, will be borne by passengers.

Both officials were in Montreal for a United Nations meeting on global aviation standards.

Restrictions were imposed on liquids and gels after British authorities uncovered a plot to blow up aircraft using liquid explosives in August 2006.

Bottle and liquids scanners have already been developed that can inspect both sealed and unsealed bottles in five seconds.

Napolitano said the technology isn't ready.

"I think that's premature," Napolitano said in an interview with The Associated Press.

The European Union says it plans to phase out restrictions on carrying liquids onto planes by 2013.

Benjamin told The AP they think they'll have the equipment in airports within two years.

Napolitano said she expects the ICAO will issue a joint declaration that will commit 190 nations to strengthen aviation security measures. She said it will be followed up with a series of regional summits that will discuss implementing measures.

Napolitano is urging other nations to use body scanners and other methods to thwart terrorists from carrying plastic and powdered explosives onto airplanes.

She said the catalyst is the failed plot to bomb a U.S. airliner last Christmas Day. U.S. authorities say a young Nigerian named Umar Farouk Abdulmutallab tried to detonate a bomb hidden in his underwear during a flight from Amsterdam to Detroit.

The Montreal meeting comes amid fears of fresh attacks in Europe. The Eiffel Tower in Paris was briefly evacuated Tuesday, the second time in the past week because of an unspecified threat.

"I can't comment on what any particular country is doing, but what I can say is that aviation continues to be a target and there continue to be threats against aviation as we saw on Christmas which is why it was important for the countries of the world to come here at ICAO and put that on the agenda and reach a resolution with respect to aviation security," Napolitano said. "It's something that's never been done."