A top US agriculture official has warned that unless countries take immediate steps to sharply boost agricultural productivity, food output and reduce hunger then the world risks fresh social instability.

In an interview with the Financial Times, Tom Vilsack, US secretary of agriculture, indicated that food security and global stability were tied, in a sign that Washington's worries about the global food crisis go well beyond its humanitarian implications.

“This is not just about food security, this is about national security, it is about environmental security,” he said on the sidelines of the first meeting of the Group of Eight ministers of agriculture. Although the US has in the past talked about the links, Barack Obama, US president, and his team have made it a priority, officials said.