The United Nations said it would start training Arab League observers working in Syria within days.
A formal request for help has been made by the Arab League, and the United Nations has agreed to start the training in Cairo after League foreign ministers meet this weekend, a UN spokeswoman, Vannina Maestracci, told AFP.
Russia and China vetoed a Western draft UN resolution in October that would have condemned Assad's regime. Russia, which is sticking by its ally, later circulated an alternative that would have blamed both sides.
On Monday Russia distributed a new draft resolution, but Western diplomats said there is no apparent change in Moscow's position opposing strong UN action.
Ban's appeal came as Assad's regime was hit by the defection of a leading MP who announced he was going into exile, along with an opposition figure who heads Syria's largest tribe.
"I have come to Turkey to activate the opposition. The Syrian revolution is our path. The country's youth are making the greatest sacrifices for a better future," Al-Baqqara tribal chief Nawaf al-Bashir told Al-Arabiya television.
MP Imad Ghaliun, a member of parliament's budget committee, told the same network he had chosen Egypt as a base to try to help achieve "freedom and dignity" for the people in a future democratic Syria.
Assad's political and military opponents have set up a liaison office and a "hotline to follow internal political developments on the ground."
The Syrian National Council, an umbrella group, said in a statement the decision was taken in talks on Saturday with the Syrian Free Army (SFA), formed of military deserters.
The talks also focused on efforts to "restructure SFA units and create a modern and flexible structure ... to allow for rapid deployment" and cope with the daily inflow of deserting officers and soldiers.
In a statement signed by its leader Riyad al-Asaad, the SFA called on the 22-member pan-Arab bloc to "quickly transfer the case of Syria to the UN Security Council."
The statement, sent to AFP in Nicosia, appealed to the international community to "act quickly against the regime through Chapter 7 of the UN charter to maintain peace" in Syria.
The SFA claims to have gathered some 40,000 fighters under its command since an anti-regime revolt broke out in Syria in mid-March. The crackdown on dissent has since cost more than 5,000 lives, the United Nations estimates.
A media adviser to a top Syrian army defector, General Mustafa Ahmad al-Sheikh, said last week that a special council is being set up to oversee all military operations.
It will "help organise defections" and will "encourage large-scale rather than individual defections," he said.
On the diplomatic front, France accused Iran of repeatedly violating a UN arms embargo with exports to its ally.
"These arms deliveries are illegal and deeply shocking because they benefit a regime that has chosen a kind of repression that the UN rights council has repeatedly said constitutes 'crimes against humanity'," said foreign ministry spokesman Romain Nadal.
At least five people including a woman were killed and nine were wounded on Monday as pro-regime "shabiha" militiamen shot up a bakery in Homs, a rights group said.
The Syrian Observatory for Human Rights also said a 16-year-old girl was fatally wounded by a sniper in Homs, and that security forces fired mortars at Baliun village in Jabal al-Zawiya where hundreds of deserters had gathered.
"Twenty soldiers defected. Five of them were killed, the 15 others were able to flee," the Observatory said in statements received in Nicosia.
The latest violence and defections came a day after Damascus announced a general amnesty for crimes committed since the outbreak of unrest last March 15.
But the opposition Muslim Brotherhood, stressing that more than 60,000 have been detained since the start of the unrest, dismissed the amnesty -- the third of its kind -- as "neither serious nor credible."
Human rights lawyer Anwar Bunni said "only hundreds" out of "thousands of people who have been detained for exercising their right to freedom of expression and peaceful demonstration" were freed.