Canada and the United States are partially easing some of the restrictions against carrying liquids and gels onto airliners, officials said Monday.

"Passengers will be permitted to bring liquids, gels, and aerosols through security screening at Canadian airports, provided that these items are packaged in a container with a capacity of 90 ml or 90 grams or less and that the containers fit comfortably in one clear, closed and resealable plastic with the capacity of no more than one litre. One bag per passenger will be permitted," Transport Canada security operations director Jean Barrette said at a news conference on Monday.

The new security measures will be implemented as of 4 a.m. ET on Tuesday.

"Passengers should place all liquids, gels and aerosols from their carry-on bags to the trays provided at the beginning of the screening process," Barrette said.

Travellers are expected to supply their own plastic bags.

However, Canadian Air Transport Security Authority will temporarily provide a short-term supply of the plastic bags for passengers uninformed of the new rules during the transition period.

In addition, passengers are banned from carrying onboard unsealed, open or opaque plastic bags of any size. They are also restricted from carrying liquids, gel or aerosols in containers larger than 90 ml or 3 ounces.

If found with the forbidden items, passengers are faced with the option of leaving them behind or going back into the public area to put their containers in their checked baggage.

When asked why the changes were being instituted now, Barrette said that officials know "a little bit more now" about what happened in August.

Tougher airport screening procedures were instituted in August around the world after British police foiled an alleged terrorist plot to assemble and detonate bombs using liquid explosives on 10 airliners flying to the United States from Britain.

"The reason for the limited quantity is based on an ongoing dialogue we have been holding (with) experts around the world to determine the specific size of containers ... to be carried onto the aircraft," said Barrette, adding that he was unable to elaborate on exactly what officials have learned.

Last week, Transport Canada announced that it was easing some of the restrictions on airport retail stores.

The sale of liquids, gels and aerosols, at all retailers -- both duty-free and non-duty-free -- located within secure areas of Canadian airports was restored for most air passengers last Friday.

Earlier rules allowed only duty-free shops to sell liquids, gels and aerosols, which were to be picked up from duty-free employees as passengers boarded their planes.

South of the border

Meanwhile, south of the border, United States officials also announced a partial lifting of their bans.

"We now know enough to say that a total ban is no longer needed from a security point of view," Kip Hawley, head of the Transportation Security Administration, told a news conference at Reagan National Airport on Monday.

Hawley told reporters that most liquids and gels that air travellers purchase in secure areas of airports will now be allowed on planes.

He called the new procedures a "common sense'' approach that would maintain a high level of security at airports but ease conditions for passengers.

The changes mean that passengers can purchase liquids at airport stores after they go through airport security checkpoints and can take the items on to their planes.

The new procedures go into effect on Tuesday.

"We've worked very closely with Canada, and I'm very pleased to say that that has borne fruit,'' said Michael Jackson, deputy secretary of Homeland Security."And today, Canada is making an announcement very much similar to ours, so that we can align our two processes at the checkpoints -- Canada and the United States -- and thereby make it easier on passengers.''

With files from The Associated Press