"The country's population has been decimated by the pandemic we all know, HIV and AIDS," Mugabe said.

"Perhaps now we need to establish whether that pandemic still has the same effect of decimating our population, or that we managed at least to control it."

According to the 2002 count, Zimbabwe's population was 11.6 million, up 1.2 million from a decade earlier.

But the growth rate slowed as AIDS erupted across the region.

After peaking at 3.98 percent in 1983, the annual population growth rate began a steady slide, bottoming out in 2007, when the population is thought to have shrunk by 0.38 percent, according to World Bank data.

Though about 13 percent of the population is HIV positive, Zimbabwe has emerged as something of an AIDS success, with new HIV infections down 50 percent between 1997 and 2007, a study last year found.

Officials are encouraging male circumcision because some research has shown the procedure can reduce HIV transmission rates.

Zimbabwe has also seen an exodus of people fleeing political and economic turmoil over the last decade, with some estimates suggesting three million people have left.

The census will cost about $40 million, with donors chipping in $12.6 million, the finance ministry said.