The UN chief told Bashar al-Assad on Sunday to "stop killing your people" and the Syrian leader offered an amnesty for "crimes" committed during a 10-month-old revolt against him.
Arab League foreign ministers will meet next Sunday to discuss the future of a monitoring mission sent last month to check if Syria is respecting an Arab peace plan.
Assad's violent response to the uprising has killed more than 5,000 people, by a UN count. The Syrian authorities say 2,000 members of the security forces have also been killed. At least 25 civilians and soldiers were reported killed on Sunday.
"Today, I say again to President Assad of Syria: stop the violence, stop killing your people. The path of repression is a dead end," U.N. Secretary-General Ban Ki-moon told a conference in Lebanon on democratic transitions in the Arab world.
Assad's amnesty will run to the end of January, covering army deserters and people who possessed illegal arms or had violated laws on peaceful protest, the state news agency SANA said.
Syria's Addounia television said Arab monitors discussed the amnesty with Damascus police on Sunday.
Opponents of Assad said the amnesty was meaningless because most detainees were held without charge in secret police or military facilities with no due process or legal documentation.
"The problem is not those who have reached trial or have been sentenced to terms in civic jails but those who are imprisoned and we don't know where they are or anything about them," said Kamal Labwani, who was freed last month after six years as a political prisoner and is now in Jordan.
The Arab League's Syria committee, whose Qatari chairman has said the observer mission has failed to staunch the bloodshed, will discuss a report by the monitors on Friday, Egypt's MENA news agency said.
The Cairo-based League will not send any more monitors to Syria before the Arab foreign ministers meet next Sunday, Mena said.
Anti-Assad protests began in March inspired by a wave of popular anger against autocratic rulers sweeping the Arab world.
Assad has issued several amnesties since the start of protests, but opposition groups say thousands of people remain behind bars and many have been tortured or abused.
The Avaaz campaign group said on Dec. 22 at least 69,000 people had been detained since the start of the uprising, of whom 32,000 had been released.
Freeing detainees was one of the terms of an Arab League peace plan which also called for an end to bloodshed, the withdrawal of troops and tanks from the streets and a political dialogue.
The movement to end more than four decades of Assad family rule began with largely peaceful demonstrations, but after months of violence by the security forces, army deserters and insurgents started to fight back, prompting fears of civil war.
An opposition group said five textile workers were killed when a bomb hit their bus in the northern province of Idlib on Sunday. Sana blamed the attack on an "armed terrorist group".
Sana also said six soldiers killed by such groups were buried in the rebellious central city of Homs.
Sunday's civilian death toll in Homs rose to 11, the British-based Syrian Observatory for Human Rights reported. It said three people were also killed in random shooting by security forces in the town of Qarqas in Quneitra province.
Live footage aired from Zabadani, a rebel-held town attacked by tanks and troops on Friday, showed Arab League monitors walking among several thousand demonstrators in the main square, where a large Christmas tree stands.
"God is greater than the oppressor," protesters shouted, while others held a large white and green flag that was Syria's national emblem before Assad's Baath party took power.
Qatar's emir, once a friend of Assad, has said Arab troops may have to step in to halt bloodletting that has gone on unchecked despite the presence of Arab League monitors sent to find out if the Arab peace plan agreed last year is working.