Kofi Annan, the U.N.-Arab League envoy to Syria, said Thursday evening he would urge President Bashar al-Assad and the opposition to stop fighting and seek a political solution. Dissidents were having none of it.

The killing has to stop and we need to find a way of putting in the appropriate reforms and moving forward, Annan, the former U.N. secretary-general, said in Cairo ahead of his trip to Damascus on Saturday, Reuters reported.

Syrian dissidents reacted with dismay and said the Assad government's repression had destroyed any prospect of a negotiated deal. More than 7,500 people have been killed in the yearlong crackdown, according to the United Nations.

We reject any dialogue while tanks shell our towns, snipers shoot our women and children and many areas are cut off from the world by the regime without electricity, communications or water, said Hadi Abdullah, contacted in the city of Homs.

Another activist told Reuters Annan's call for dialogue sounded like a wink at Bashar that would only encourage Assad to crush the revolution.

U.N. humanitarian chief Valerie Amos, on a separate mission to Syria, said she was devastated by the destruction she had seen in the Baba Amr district of Homs, and wanted to know what had happened to its residents, who endured a 26-day military siege before rebel fighters withdrew a week ago.

But the visit by Amos, a former British Cabinet minister, was scorned as useless by an opposition figure.

To tell the truth, we know that Valerie Amos is useless. We have had one year of killing, shooting and bombing and nobody has moved a finger, an activist who calls himself Abo Abdo told the British newspaper The Independent. 

For her to come for 45 minutes and then to leave again is nothing. It was useless. This should have happened after the first month of the revolution. Valerie Amos's trip was the most extensive step they [the UN] has made, but it is too late. This should have happened 10 months ago, he said.

Nadir el-Hosseini, a refugee who fled to the Lebanese border after Syrian troops overran Baba Amr, told The Independent that diplomatic efforts to halt the crackdown had failed.

 I think Kofi Annan's visit will extend the life of the crisis, he said during a telephone interview. To have dialogue with a leader, he has to be legitimate. This regime is not legitimate. There is only one language they understand, and that is force.

Annan also warned the international community against arming Syrian rebels, pointing to last year's experience of arming the Libyan opposition, the Voice of America reported.

I hope that no one is thinking very seriously of using force in this situation. I believe any further militarization will make this situation worse. We have to be careful that we don't introduce a medicine that's worse than the disease, and we don't have to go very far in the region to find an example of what I'm talking about, said Annan.

As world pressure on Syria mounted, the deputy oil minister announced his defection, the first by such a senior civilian official since the start of the uprising. Abdo Hussameldin, 58, said he knew his change of sides would bring persecution on his family.

Two rebel groups later said four more high-ranking military officers had defected over the past three days to a camp for Syrian army deserters in southern Turkey.

Lt. Khaled al-Hamoud, a spokesman for the Free Syrian Army, told Reuters by telephone the desertions brought to seven the number of brigadier generals who had defected.

In Damascus, the authorities continued to crack down on Assad opponents, with government forces shooting and wounding three mourners at a funeral for an army defector that turned into a protest against the president, locals said.

Opposition sources and residents say protests in the capital are driven by inflation and the plunging value of the Syrian pound.

The world has failed to stop an unequal struggle pitting mostly Sunni Muslim demonstrators and lightly armed rebels against the armored might of Assad's 300,000-strong military, secret police and feared Alawite militiamen.

Western powers have shied away from Libya-style military intervention in Syria.

U.S. Defense Secretary Leon Panetta on Wednesday defended U.S. caution about military involvement, especially without international consensus on Syria, but said the Pentagon had reviewed U.S. military options.

Tunisia and Turkey, a neighbor of Syria, have also declared their opposition to intervention by any force from outside the region.

But Syrian dissidents said diplomatic initiatives had proved fruitless in the past. When they fail no action is taken against the regime and that's why the opposition has to arm itself against its executioner, said one rebel army officer.

Russia, a staunch defender of Syria, said Assad was battling al-Qaida-backed terrorists including at least 15,000 foreign fighters who it said would seize towns if Assad troops withdraw.

The flow of all kind of terrorists from some neighboring countries is always increasing, Russia's deputy ambassador Mikhail Lebedev said in Geneva.

The Libyan government denied Russian accusations that it was running camps to train and arm Syrian rebels.

On the ground, the humanitarian situation appeared dire. The United Nations said it was preparing food supplies for 1.5 million Syrians as part of a 90-day emergency plan.

More needs to be done, John Ging of the U.N. Office for the Coordination of Humanitarian Affairs, which is headed by Amos, told a Syria Humanitarian Forum in Geneva.