Syria's efforts to step up food purchases are being thwarted by sellers unwilling to risk delays in payments from frozen foreign bank accounts, Reuters said.

Civil war and a deepening humanitarian crisis have prompted the government of President Bashar al-Assad to issue a series of tenders for sugar, wheat, flour and rice in recent weeks.

The country needs to import around 2 million metric tons of wheat this year as civil war has sliced its crop to a near-30 year low at 1.5 million metric tons, less than half the pre-conflict average.

State buyers said payment for purchases via tenders would be made from the government's frozen accounts abroad with waivers obtained from countries that have imposed financial sanctions.

But international traders are showing little enthusiasm for the proposed payment system.

Food is not covered by international sanctions, but banking restrictions and asset freezes imposed by Washington and Europe, as well as civil war have made it difficult for some trading houses to do business with Damascus.