The government is partially lifting its ban against carrying liquids and gels onto airliners, instituted after a plot to bomb jets flying into the United States was foiled, officials said Monday.

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

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He said that most liquids and gels that air travelers 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.

That means that after passengers go through airport security checkpoints, they can purchase liquids at airport stores and take them onto their planes. The new procedures go into effect on Tuesday, Hawley said.

The new security regimen is for an indefinite period and will take effect Tuesday morning, officials said.

Tougher airport screening procedures were put in place in August after British police broke up a terrorist plot to assemble and detonate bombs using liquid explosives on airliners crossing the Atlantic Ocean from Britain to the U.S.

At the time, the Homeland Security Department briefly raised the threat level to "red," the highest level, for flights bound to the United States from Britain. All other flights were at "orange" and will remain at orange, the second-highest level, for now.

New procedures also were announced for toiletries and products like lip gloss and hand lotion that passengers bring to the airport. Previously, those liquids have been confiscated at security checkpoints. Now, these products will be limited to 3-ounce sizes and must fit in a clear, 1-quart size plastic bag. The bags will be screened and returned if they are cleared.

"Obviously, there's been a lot of unhappiness," said Richard Marchi, senior adviser to the Airports Council International, an airport trade group. "They're right to find a way to ease the burden and maintain a reasonable level of security."