As deputy oil minister Abdo Hussameldin defects from President Assad's government, Britain's ambassador to Syria tells Channel 4 News the minister's defection won't be the last.

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Abdo Hussameldin announced that he would abandon President Bashar al-Assad's regime via a YouTube video - becoming the first high-ranking civilian official to abandon the regime since the start of the uprising. His strongly-worded announcement marks a rare departure from the position taken by the government and the ruling Baath Party, which has so far remained largely loyal since the start of the bloody uprising some 11 months ago.

Although the video's veracity has yet to be confirmed, it is widely expected to be authentic.

"I Abdo Hussameldin, deputy oil and mineral wealth minister in Syria, announce my defection from the regime, resignation from my position and withdrawal from the Baath Party," he said in the video.

"I join the revolution of this dignified people. I say to this regime: you have inflicted on those who you claim are your people a whole year of sorrow and sadness, denying them basic life and humanity and driving Syria to the edge of the abyss," he said.

Speaking in London, the British Ambassador to Syria Simon Collis said that he did not think Mr Hussameldin's defection would be the last and that the regime was fragile and could collapse quite suddenly.

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Mr Collis said that he thought President Assad only had "twenty per cent support among the syrian people, perhaps a little more." He added that among minority groups and those in the major cities, President Assad was maintaining limited support because people were uncertain about what the alternative was:

"One of the challenges facing the opposition is to present an even clearer message about what they think a future Syria would like and to make clear to all of Syria's citizens that they would have a place in that future."

Mr Collis rejected any idea of the British government supplying arms to the rebels, but said: "There are other things that can be done to support the opposition, politically and in practical ways - not all of them are being made public."

Flashpoint

The deputy oil minister's resignation came as UN humanitarian chief, Valerie Amos, witnessed scenes of devastation and near desertion on Wednesday when she visited the now infamous Baba Amr district of Homs.

The suburb has become a flashpoint of the uprising, and was shelled by Syrian government military forces for nearly a month after becoming a rebel holdout.

"It was like a closed-down city and there were very few people around," Amanda Pitt, a spokeswoman for the UN Office for the Coordination of Humanitarian Affairs said of Ms Amos' visit to Baba Amr. "It looked like it was devastated from the fighting and shelling."

Meanwhile, in further evidence that pressure on President Assad to end the brutal uprising is mounting, China's envoy to Syria told the government to stop violence immediately and help the United Nations and International Committee for the Red Cross send aid to strife-hit areas.

China and Russia were the two powers which vetoed a UN security council calling for the end of the regime last month.

A spokesman for the Chinese Foreign Ministry, Liu Weimin, told reporters that the envoy, Li Huaxin, had also promoted Beijing's backing for a mediation process between the Syrian government and opposition groups facilitated by the UN and the Arab League.