The time frame for the phase would be ambitious in the most peaceful of circumstances, he said, but the current conditions make it "an operation the likes of which, quite simply, have never been tried before."
Syrian commitment is key, says Ban
Syria, which has said it will cooperate with the international mission, has made a declaration of its chemical weapons sites.
Ban said the success of the joint mission would "first and foremost" depend on a "sustained, genuine commitment" from the Syrian government to fulfill its obligations under the Chemical Weapons Convention and cooperate with the inspectors.
He also called for any states with influence over the various sides in the conflict to support the international mission and ensure the safety of its personnel. The only way to bring an end to the "appalling suffering" of the Syrian people and end the crisis is through a political, not military, process, Ban added.
U.S. Secretary of State John Kerry and Russian President Vladimir Putin discussed Syria in a 15-minute conversation Tuesday on the sidelines of the Asia Pacific Economic Cooperation in Indonesia.
The pair spoke about the U.N. resolution on destroying Syria's chemical weapons, according to a senior State Department official, as well as the need to move forward on scheduling peace talks in Geneva, Switzerland, involving all parties in the conflict.
There has been some skepticism over whether Syria will give up its entire chemical weapons arsenal.
A defected Syrian brigadier general, Zaher al-Sakat, told CNN's Christiane Amanpour last week that in addition to four secret locations within Syria, the regime is currently transferring chemical weapons to Iraq and Lebanon, an allegation that the commander of the opposition Free Syrian Army, Gen. Salim Idriss, also recently made to Amanpour. Iraq and Lebanon have denied the claims.
The U.N. resolution, which capped a month of dramatic diplomacy, was based on a deal struck between the United States and Russia that averted an American military strike over allegations the Syrian government used sarin nerve gas in an August 21 attack on a Damascus suburb.
U.S. officials said at least 1,400 people died in the attack. Syria denied responsibility, blaming rebel forces.