"Diplomacy should be given a chance, and peace given a chance," Ban said. "It's important that all the differences of opinions should be resolved through peaceful means and through dialogue."
The U.N. inspectors toured the eastern Damascus suburb of Zamalka on Thursday, according to anti-regime activists and amateur video.
In one of the videos, the inspectors stood next to their U.N. vehicles, and the accompanying caption indicated Thursday's date and the location. In another video, the U.N. convoy was seen driving through a street, accompanied by armed rebels in pickup trucks.
The U.N. team did not issue a statement about its plans Thursday.
On two previous tours this week, the inspectors visited a western suburb of the city as well as Zamalka where they took biological samples from suspected victims. Ban has said the samples would be analyzed and presented to the U.N. Security Council.
In countries neighboring Syria, governments began taking precautions against possible Syrian retaliation.
Israel has called up reservists and deployed missile defense batteries in preparation for a possible Syrian response to an American attack.
In Turkey, the government's crisis management center said on Twitter that a team of 100 chemical weapons experts were sent to the border area, which was being screened for any signs of chemical attacks.
Turkey is Assad's strongest critic and has backed Syria's opposition and rebels. The country said this week it would take part in any international coalition that would move against the Syrian government.
Laub reported from Beirut. Associated Press writers Yasmine Saker in Beirut, Tia Goldenberg in Jerusalem, Gregory Katz in London and George Jahn in Vienna contributed reporting.
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