He said the US Central Intelligence Agency had calculated the farmland area per capita for a number of countries with populations of more than 100 million.
He said the area of farmland for the world's population was currently 1.41 ha per person.
Mr Miller said countries with less than 0.82 ha per capita tended to be net importers of food.
China had a farmland area of 0.64ha/capita, while for India, it was 0.74ha/capita.
Mr Miller said the task was to provide enough grain for sub-Saharan Africa, north Africa, the Middle East, south Asia and east Asia, where food deficits exceeded the ability of nations within those regions to provide for themselves.
In 2007, countries in east Asia had to import 47.2 million tonnes to satisfy their needs, while Middle East nations imported 32.6 million tonnes.
In northern Africa, 29.5 million tonnes of grain had to be imported, with countries such as Egypt and Sudan the big buyers.
"The challenge for us all is how do we take care of the needs of net food importers," Mr Miller said.