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.
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.
"Today, I say again to President Assad of Syria: stop the violence, stop killing your people. The path of repression is a dead end," UN Secretary General Ban Ki-moon told a conference in Lebanon on democratic transitions in the Arab world.
"From the very beginning of the … revolutions, from Tunisia through Egypt and beyond, I called on leaders to listen to their people," Ban said. "Some did, and benefited. Others did not, and today they are reaping the whirlwind."
Syrian state news agency SANA said Assad had granted an amnesty for "crimes committed in the context of the events since 15 March, 2011, until 15 January, 2012." It gave no details.
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 that many have been tortured or abused.
The Avaaz campaign group said on 22 December that 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 peace plan, which also called for an end to bloodshed, the withdrawal 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.
Arab intervention?
Qatar's emir, once a friend of Assad, has said Arab troops may have to step in to halt the 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.
Asked if he was in favor of Arab nations intervening in Syria, Qatari Emir Sheikh Hamad bin Khalifa al-Thani told the US broadcaster CBS: "For such a situation to stop the killing … some troops should go to stop the killing."
The emir, whose country backed last year's NATO campaign that helped Libyan rebels topple Muammar Qadhafi, is the first Arab leader to propose Arab military intervention in Syria.
CBS said on its website that the interview would be broadcast in its "60 Minutes" program later on Sunday.
Qatar's prime minister heads the Arab League committee on Syria and has said killings have not stopped despite the presence of Arab monitors sent there last month.
The League is due to hear a report from the monitors on Thursday and decide whether their mission should continue.
In the preview of the interview on the website, the emir did not spell out how any Arab military intervention might work.
There is little appetite in the West for any Libya-style intervention in Syria, although France has talked of a need to set up zones to protect civilians there.
China and Russia have blocked any action against Syria by the UN Security Council. The United States, the European Union and the Arab League have announced economic sanctions, although it is not clear if the Arab measures have been implemented.
Turkey, whose foreign minister was also attending the conference where Ban spoke in Beirut, has also slapped sanctions on Syria after the violence prompted it to turn against a neighbor it had once courted assiduously.
In the latest violence, residents said security forces shot dead a 17-year-old protester in the Damascus neighborhood of Qaboun overnight. "He was hit in the chest," one resident said.
