The US announced an infusion of humanitarian aid to Syria on Thursday, just as the head of the UN-backed mediation effort between the country’s warring forces resigned.Kofi Annan – a former UN secretary-general – as special UN envoy to Syria, spent months mediating a ceasefire between Syrian President Bashar Assad and the opposition forces that failed to take hold or show any results on the ground.The White House announced $12 million in additional humanitarian assistance for a total of $76m. that the US has shelled out for food, water, medical supplies and other necessities over the course of the 17-month-old conflict.“The quickest way to end the bloodshed and suffering of the Syrian people is for Bashar Assad to recognize that the Syrian people will not allow him to continue in power and to step aside,” the White House said in its statement, adding, “We will continue to work with the opposition and our allies and partners to support an inclusive transition that guarantees the Syrian people their universal rights.”The grinding humanitarian crisis has served as a sign that the cease-fire Annan pursued failed to materialize, with the violence only increasing on his watch.“Kofi Annan deserves 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,” UN Secretary- General Ban Ki-Moon said, in announcing Annan’s resignation.Talks are under way to find a successor.Annan blamed “fingerpointing and name-calling” at the UN Security Council for his decision to quit, but suggested his successor may have better luck.“There may be other plans, other approaches that may work quite effectively,” he said, adding that at this stage, the focus should still be on a political transition that means “Assad will have to leave sooner or later.”Russia and the US have clashed repeatedly at the Security Council, with the US looking to hasten Assad’s departure and Russia standing by its Arab ally.Syria expressed disappointment that Annan was going, as did Russia.“We understand that it’s his decision,” Vitaly Churkin, Russian ambassador to the UN, told reporters. “We regret that he chose to do so. We have supported very strongly Kofi Annan’s efforts. He has another month to go, and I hope this month is going to be used as effectively as possible under these very difficult circumstances.”Churkin added he was encouraged that Ban was looking for a successor to Annan.The UK, which, like America, wants Assad to resign, said the move showed that the mediation process was not working.The White House said Annan’s decision to quit had highlighted Assad’s failure to meet his promise to abide by the cease-fire plan, and added that it continued to believe that “Assad must go.”Annan’s decision to abandon the role comes amid a report by Reuters that the US is secretly helping the rebels.Anonymous US officials told Reuters that US President Barack Obama has signed a secret order authorizing support for rebels seeking to depose Assad, though they did not disclose the exact nature of the assistance other than to rule out the provision of lethal weaponry.The order, approved at some point earlier this year and known as an intelligence “finding,” broadly permits the CIA and other US agencies to provide support that could help the rebels oust Assad.A US government source also told Reuters that under provisions of the presidential finding, the US was collaborating with a secret command center operated by Turkey and its allies.Publicly, the US on Thursday ramped up its efforts to alleviate the suffering of civilians affected by the fighting.