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WASHINGTON - President Obama has formally authorized American shipments to Syria of non-lethal equipment and supplies specifically aimed at countering the threat of Bashar al-Assad's chemical weapons as the world waits for them to be neutralized.

In a signed order, Obama today waived prohibitions of such shipments by the Arms Export Control Act, determining that the assistance is "essential to the national security interests of the United States."

The materials - including chemical weapons-related personal protective gear and medical supplies - will be sent to "vetted" members of the Syrian opposition, international aid groups inside Syria, and any other organizations working to "prevent the preparation, use, or proliferation of Syria's chemical weapons," an administration official said.

Among the groups expected to receive the aid is the Organization for the Prohibition of Chemical Weapons, the group expected to lead any monitoring and enforcement effort under the deal to transfer stockpiles under international control.

An administration official said the authorization has been in the works since before the massive Aug. 21 chemical weapons attack. This aid is separate from the lethal and other assistance the U.S. has been shipping to Syria.