Australia will pledge an extra $25 million in aid to Iraq and Syria, where millions of men, women and children are enduring a worsening humanitarian tragedy.
US Secretary of State John Kerry described the scenes in Syria as reminiscent of the aftermath of World War II. 
Australia's Foreign Affairs Minister Julie Bishop is to make the aid pledge at a gathering of donors in London on Thursday, which has widened into a forum discussing how the country can possibly recover from its civil war.
She will also announce that Australia will deploy 10 Australian Civilian Corps specialists to Jordan and Lebanon. They will work in education, protection, water, sanitation and logistics projects.
At a meeting in Rome on Tuesday, attended by foreign ministers from the "small group" coalition, including Australia, fighting against Islamic State, Mr Kerry said the humanitarian crisis in Syria was "getting worse by the day, not better".
More than 13 million Syrians were urgently in need of aid, of whom 6 million were children, he said. Hundreds of thousands were trapped in areas where food deliveries were rare and non-existent.
"We are not talking about remote areas miles out in the desert - the town of Madaya is one hour's drive from Damascus, yet in recent months its people have been reduced to eating grass and leaves," he said.
They were besieged by forces of the Assad regime deliberately preventing them from receiving supplies and support, Mr Kerry said, adding that this was "against the rules of law".
"Eyewitnesses have described 'walking skeletons'."
These were scenes not seen in these numbers and this "organised way" since the concentration camps were liberated after World War II, Mr Kerry said.
He is to attend the Supporting Syria meeting in London on Thursday alongside world leaders.
The meeting is being billed as a "donors conference" raising money for humanitarian aid. However, due to the level of political interest, it will include discussions about how the country may be rebuilt more generally.
In a speech to the conference, Ms Bishop will call for a serious negotiation leading to a ceasefire as a prelude to lasting peace.
"Countries with influence on these parties must also act responsibly and bring pressure to bear on the warring parties," she will say.
"We welcome the focus here today on economic and education opportunities, as well as building economic resilience and facilitating development in refugee host countries Jordan, Lebanon and Turkey.
"It is vital that Syrian refugees have the opportunity to contribute to their host countries and the communities within, and be given the opportunity to develop the skills necessary to help rebuild their country after the conflict is over."