The United Nations is to start training Arab League observers monitoring the crackdown in Syria within days.
A formal request for help has been made by the Arab League and the UN has agreed to start the training in Cairo after League foreign ministers meet this weekend, according to a UN spokesman. Training will be carried out by staff of the UN High Commissioner for Human Rights.
"At the request of the League of Arab States, the OHCHR has agreed to train observers and will deploy to Cairo to do this training," a UN spokesman said.
A report by the observer mission is to be handed over to Arab League ministers on Thursday and the ministers will meet on Saturday in Cairo to decide the future of the mission.
The spokesman said the training had been scheduled to start earlier but was delayed at the request of the Arab League until after the ministerial meeting.
The UN said in early January that it was ready to help the observer mission, which has faced widespread criticism from the Syrian opposition, but that it was waiting for a request from the Arab League.
The announcement came as the regime of President Bashar al-Assad suffered a series of defections, handing the opposition a propaganda coup amid growing demands for international intervention.
Following the flight to Turkey of a brigadier-general, Mustafa Ahmed al-Sheikh, a second military leader was filmed announcing his defection to opposition supporters inside the country.
In a clip posted to YouTube, he is shown wielding his identity card to a cheering crowd standing in front of the green, white and black new revolutionary flags of the opposition as he says he is joining them.
That took place in Homs province, the epicentre of the uprising, and one of whose members of parliament, Imad Ghalioun, announced from Cairo he was also leaving in protest.
"The Syrian people are living their worst period," Mr Ghalioun told the Al-Arabiya news channel. "The people of Homs are under siege and the city is disaster-stricken. There is no electricity, piles of garbage fill the streets.
"The sounds of shelling all night terrify children."
Diplomats, analysts and even members of the opposition insist that Mr Assad's power base is under no direct threat. After arriving in Turkey, which has become the base of the opposition Free Syrian Army, Gen. Sheikh said he estimated 20,000 soldiers had defected from a total army strength of near 300,000.
That figure is half the number claimed by the FSA's founder, Col Riad al-Assad, as having joined his group.
However, there are unmistakable signs of Mr Assad's grip failing. Parts of Homs province and the northern province of Idlib are clearly under rebel control, insofar as they are under regular attack from the military, though the opposition is unable to establish the sort of control exercised by renegade cities in Libya last year.
His forces raided Aleppo University on Sunday night after a protest by students there. The city, Syria's second largest and most loyal, has so far proved most immune to protest.
Amr al-Azm, a Syrian exile and academic in the United States, said Mr Assad's increasingly belligerent tone, despite occasional offers of amnesties such as one on Sunday, meant a long-drawn out civil war was the most likely outcome.
"The regime is set on war and the opposition is arming up," he said. "If the Arabs want to avoid a total fracturing of Syria they have to intervene either way: send troops in or let someone else do it."
The Arab League is to meet on Saturday and Sunday to discuss the findings of its peace monitoring mission to the country. It has so far ruled out seeking United Nations support, but that might change, particularly after Sheikh Hamad bin Khalifa al-Thani, the Emir of Qatar, called at the weekend for Arab troops to be sent to intervene.
Ban Ki-moon, the United Nations secretary-general, made an unusual appeal for action by his own Security Council, which has so far been prevented from taking a position by Syria's strategic allies, Russia and China.
"The situation has reached an unacceptable point," he said at an energy summit in Abu Dhabi also attended by the Chinese prime minister, Wen Jiabao. "I sincerely hope that the Security Council will handle this in a sense of seriousness and gravity and in a coherent manner."