"This amounts to an execution order for killing 1.7 million people under famine, especially during this harsh wintertime," Syrian National Coalition President Hadi al-Bahra said at a press conference in Copenhagen.
"Sixty percent of them are children and women and we don't understand as Syrians how the international community would allow starving 1.7 million under their watchful eyes," he added, visibly emotional.
The UN World Food Programme (WFP) was forced this week to cut off food aid to 1.7 million Syrian refugees due to a $64 million (51 million euros) shortfall in funding from donors.
The agency has launched a social media campaign to try to convince 64 million people to donate $1 each in a desperate bid to come up with the cash needed to feed the Syrian refugees.
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The Syrian National Coalition is considered by the US and other key powers to be the main body representing the opposition, but it has little power inside Syria where disparate militant groups outside its control hold sway.
The exiled group's leader said a US-funded plan to train and equip moderate Syrian rebels would take months to implement and that the anti-regime Free Syrian Army (FSA) would have to look for funding elsewhere in the meantime.
"It is expected to start by the end of February or the end of March which is a very long time to leave the Free Syrian Army at current levels of assistance," al-Bahra said.
"So they have to find a way of increasing the help and equip part of the programme to start earlier," he added.