Four million Syrians, or a fifth of the population, are unable to produce or buy enough food for their needs and the situation could deteriorate further next year if the two-year old conflict continues, the United Nations said on Friday.

Following a visit to Syria between May and June, the UN Food and Agriculture Organization (FAO) and the World Food Programme (WFP) said in a report that domestic production over the next twelve months is likely to be severely compromised.

The agencies estimated Syria would need to import 1.5 million metric tons (1 metric ton = 1.1023 tons) of wheat for the 2013/14 season. Wheat production has fallen to 2.4 million metric tons, some 40 percent less than the annual average harvest before the conflict of more than 4 million metric tons , they said.

Syrian President Bashar Assad on Thursday said he and his government would survive the civil war, having endured everything his opponents could do to topple him and only the distant prospect of direct foreign military intervention could change that.

After steady rebel gains in the first two years of civil war, Syria became stuck in a bloody stalemate lasting months until a June government offensive that led to the capture of a strategic border town. Momentum now looks to be behind Assad.

"This was their goal in hitting our infrastructure, hitting our economy, and creating complete chaos in society so that we would become a failed state," Assad said in an interview with Syria's official Thawra newspaper published on Thursday.

"So far we have not reached that stage."

The only factor that could undermine the resilience of the government, he said, was direct foreign intervention. But he said that was a unlikely due to foreign powers' conflicting views of an opposition movement increasingly overtaken by radical Islamist militants.