More than 2.5 billion people worldwide still lack access to improved sanitation and nearly 1.2 billion people practice open defecation, posing a major health threat to their communities, according to a United Nations report released on Thursday.

Poor sanitation threatens children's survival as a faecally-contaminated environment is directly linked to diarrhea disease, one of the biggest killers of infants, said the report, issued jointly by the United Nations' Children's Fund (UNICEF) and the World Health Organization (WHO).

A clean environment is very difficult to ensure if open defecation is practiced, even by a minority of the population, thereport said.

"At current trends, the world will fall short of the Millennium(Development Goals) sanitation target by more than 700 million people," said Ann Veneman, UNICEF executive director, in a statement.

"Without dramatic improvements, much will be lost," she added.

The report showed some progress in access to improved drinking water sources. At present, 87 percent of the world's population can access improved water sources with the figure expected to riseto 90 percent by 2015.

The number of people defecating without sanitary facilities – a practice known as open defecation – has also fallen.

But worldwide 18 percent of the population, totaling 1.2 billion people, still practice it. In southern Asia, some 778 million people still rely on this riskiest sanitation practice.

"We have today a full menu of low-cost technical options for the provision of sanitation in most settings," said WHO Director-General Margaret Chan.

"More and more governments are determined to improve health by bringing water and sanitation to their poorest populations. If we want to break the stranglehold of poverty, and reap the benefits for health, we must address water and sanitation," she stressed.

(Xinhua News Agency July 18, 2008)