BEIRUT/ALEPPO: Former U.N. Secretary-General Kofi Annan has quit his post as international peace envoy to Syria, shooting down hopes for a diplomatic resolution to the increasingly bloody conflict.

Annan denied this resignation meant the Syrian people would be left to fend for themselves as battles raged in Aleppo, killing at least 60 people.

Annan, who’s mission, centered on an April cease-fire that never took hold, blamed “finger-pointing and name-calling” at the U.N. Security Council for his decision to quit, but suggested his successor may have better luck.

“I did not receive all the support that the cause deserved,” Annan told a hastily scheduled news conference in Geneva. He said “continuous finger-pointing and name-calling” in the Security Council had hindered his attempts to implement the so-called six-point peace plan.

“The increasing militarization on the ground and the lack of unanimity in the Security Council fundamentally changed my role,” the former U.N. chief said.

“You have to understand: As an envoy, I can’t want peace more than the protagonists, more than the Security Council or the international community for that matter.

Predicting that Syrian President Bashar Assad would go “sooner or later,” Annan did not rule out his successor having more luck or success, despite his warning there was “no plan B.”

“The world is full of crazy people like me so don’t be surprised if someone else arrives to take it on,” he said, adding that “the international community can do a lot more if they were to work in concert to bring sustained pressure” on the various parties involved.

Diplomatic efforts looked increasingly irrelevant as fighting has intensified in Aleppo, Damascus and elsewhere. World powers have watched with mounting concern Annan’s mediation effort faltered, and violence that has already claimed an estimated 18,000 lives worsens.

U.N. chief Ban Ki-moon in New York said that Annan would go at the end of the month, adding the envoy deserved “our profound admiration for the selfless way in which he has put his formidable skills and prestige to this most difficult and potentially thankless of assignments,” Ban said. Talks were under way to find a successor.

Syria expressed “regret” that Annan was going. In a statement, the Foreign Ministry said “Syria always proved it was totally engaged in the [Annan] plan,” and accused “countries that seek to destabilize Syria” of having “hindered and continued to hinder” the former U.N. chief’s mission.

The U.S. and Russia, a key ally of Damascus, exchanged blame for the decision. “Kofi Annan is an honorable man and a brilliant diplomat, so I regret that very much,” said Russian President Vladimir Putin, who called the events in Syria a “tragedy.”

Alexei Pushkov, head of the foreign affairs committee in the lower house of the Russian parliament, blamed the failure of Annan’s plan on the West.

“Regrettably, the so-called Friends of Syria led by the United States have encouraged the opposition and sought to put pressure only on the Syrian government. That became the reason behind the failure of Annan’s plan,” Pushkov said, according to RIA Novosti.

The U.S. blamed the resignation on the refusal of Russia and China to back U.N. resolutions targeting Assad.

“His resignation highlights the failure in the United Nations Security Council of Russia and China to support meaningful resolutions against Assad that would have held Assad accountable for his failure to abide by the Annan plan,” White House spokesman Jay Carney told reporters aboard Air Force One.

In further signs of failed diplomacy, Putin and British Prime Minister David Cameron failed to hide their differences over Syria during a landmark London meeting before the two leaders watched the Olympic judo together.

On his first visit to Britain for seven years, Putin pledged to work with Cameron to bring Syria’s bloody 17-month conflict to an end.

But after 45 minutes of talks at his Downing Street residence, Cameron acknowledged there was still a gulf between their stances. “There have been some differences in the positions that we’ve taken over the Syrian conflict,” he told reporters.

In New York, the U.N. General Assembly was expected to vote Friday on a resolution drafted by Saudi Arabia, which backs the rebels. Arab countries diluted the resolution, dropping a demand that Assad resign, but nevertheless, Russia said it would not back the resolution because it was “unbalanced” and would encourage rebels to keep fighting.

In Syria, the fight for Aleppo, the latest battlefield, intensified as fighters fought government forces using warplanes and artillery in battles that have lasted 12 days. Heavily armed government troops are trying to drive a few thousand rebel fighters from the city in battle whose outcome could be a turning point in the conflict.

In one of the first indications the rebels are starting to deploy heavy weapons against the Syrian army, rebels turned a captured government tank’s gun on the Menakh airfield 35 km north of the city – a possible staging post for army reinforcements and a base for war planes and helicopter gunships.

“We hit the airport using a tank that we captured from the Assad army. We attacked the airport a few times but we have decided to retreat at this time,” a rebel fighter named Abu Ali told Reuters.

In Damascus, activists and residents reported the regime had unleashed new raids against opposition fighters, killing at least 35 people, mostly unarmed civilians.

Activists said at least 20 people were killed in the Palestinian camp of Yarmouk after government forces shelled a gathering of people in Jaouneh Street, bordering Tadamon.

“They bombed street, then when people gathered in the place they sent them another shell. There is blood and body parts everywhere,” a resident told The Daily Star via Skype.

Around 60 people were killed in Syria Thursday, 43 of them civilians, according to the British-based opposition Syrian Observatory for Human Rights.

The lightly armed insurgents are battling a well-equipped army that has overwhelming superiority on paper. But the rebels have managed to capture some tanks and heavy weapons and their ranks are swelled by army defectors. The rebels are consolidating areas they control in Aleppo, attacking police posts and minor military installations. They claim to have seized three police stations this week.

Reuters correspondents heard heavy weapons fire Thursday morning from Salaheddine in southwest Aleppo, a gateway to the city that has been fought over for the past week. Although government forces have made concerted efforts to take Salaheddine, a full-out assault on the city as a whole has yet to take place.

Mobile phone connections have been cut since Wednesday evening, leading to speculation among residents that an increase in military action might be imminent.

Some 2.5 million Aleppo residents are now caught up in battle zones, facing shortages of food, fuel, water and cooking gas. Thousands have fled and hospitals and makeshift clinics can barely cope with casualties.

The U.N. Food and Agriculture Organization said up to three million Syrians are likely to need food and other aid in the next 12 months because the conflict has prevented farmers from harvesting their crops.

Syria meanwhile accused Turkey of backing terrorism by opening its airports and borders to Al-Qaeda to carry out attacks inside Syria.

“The Turkish government plays a fundamental role in supporting terrorism by opening its airport and borders to host Al-Qaeda elements, jihadists and Salafists,” Syria’s Foreign Ministry said in a statement circulated on state television.