As international delegates head into day two of the Geneva II peace conference in Montreux, Switzerland, World Vision is calling on world leaders to ensure that humanitarian aid is able to reach the most vulnerable people in Syria.

The long-awaited summit is being joined by representatives from Syria's government and its opposition alliance, as well as 40 countries, to negotiate peace. The UK's Foreign Secretary William Hague is among the delegates.

It marks the first time that members of opposing Syrian factions have come together since civil war broke out following an uprising against the Assad regime in 2011.

It is hoped that delegates will be able to negotiate a ceasefire and begin to put steps in place to bring reconciliation and hope to a land torn apart by brutal violence and civil unrest.

However Jules Frost, a senior humanitarian advisor for World Vision, has warned that this could take some time.

"Agreeing a negotiated peace at Geneva II won't be easy," she said. "However, parties to the conflict must abide by their obligations under International Humanitarian Law and ensure humanitarian aid reaches all those in need.

"We have seen where there's a will, there's a way. It is shameful that while access to remove chemical weapons can be gained, the same cannot be done to save the lives of millions of innocent children and their families."

UN Secretary-General Ban Ki-Moon, who has warned delegates they face "a formidable challenge", has branded a failure to end the conflict in Syria as "unforgivable".

The violence has left over 100,000 people dead and 9.5 million displaced, and as refugees flee to neighbouring countries such as Lebanon, Jordan and Turkey, there are fears of further instability across the already fractured Middle Eastern region.

World Vision, along with many international aid organisations, says that children are often among the worst affected by such outbreaks of violence. Following the devastation of Typhoon Haiyan in the Philippines the charity warned that statistically, violence against women and children increased during and in the aftermath of emergencies.

It has been raising significant concern about the welfare of Syrian children caught up in the crisis throughout the past three years of unrest.

World Vision is calling for an urgent humanitarian intervention.

"If the parties to the conflict cannot agree a comprehensive ceasefire at Geneva II talks, we need them to negotiate temporary cessations of hostilities in certain areas to allow convoys to move and the injured and malnourished to be evacuated," explains Ms Frost.

Chief Executive of World Vision UK, Justin Byworth, has said the need for action in Syria is "urgent", and criticised the international community's slow response.

"Despite a statement from the UN Security Council in October in October on improving humanitarian access for Syrians, especially critical for hard to reach and besieged areas, progress has been poor," he said.

Quoting the UK International Development Secretary, Justine Greening, he has claimed "there are no excuses" for this weak response.

"If the parties meeting in Geneva cannot agree to cease hostilities and remove bureaucratic delays, they will leave themselves open to the accusation that they are using starvation as a weapon of war," he concluded.

Pope Francis has spoken of his desire to see a quick and peaceful resolution to the conflict in Syria reached during the Geneva II talks.

"I pray that the Lord may touch the hearts of all so that, seeking together the greater good of the Syrian population, so sorely troubled, they may spare no efforts in urgently bringing to an end the violence in this conflict that has already caused too much suffering," he said.

"I hope that the dear Syrian nation may embark on a decisive path towards reconciliation, concordance and restructuring with the participation of all citizens, so that each person may regard his peers not as enemies of competitors, but rather as brothers to be welcomed and embraced.

The peace summit will continue in Montreux until Friday, when it will move to Geneva.