"However, the fact remains that a comprehensive and decisive response to the global challenge of mercury is not in place and this needs to be urgently addressed," Achim Steiner, the head of Nairobi-based UNEP, said in a statement.

Exposure to mercury -- sometimes called quicksilver -- can damage the brain, nervous system and foetuses.

Western nations have slashed its usage, but activists say poorer countries increasingly rely on it for processes including small-scale gold mining.

UNEP is hosting a week-long meeting of governments and experts that began in Thailand on Monday to discuss how to reduce environmental sources of mercury.

Steiner said the world was demanding fast action.

"There is no real reason to wait on many of the mercury fronts. Viable alternatives exist for virtually all products containing mercury and industrial processes using mercury."

Scores of environment ministers meeting in Kenya in February agreed to phase out mercury use, but stopped short of a legally binding treaty imposing tough targets that had been demanded by anti-mercury campaigners and the European Union (EU).

Activists blamed a group of countries led by the United States, which rejected the idea of a binding treaty, preferring what it said were more flexible voluntary partnerships aimed at helping developing nations cut their use of the toxic metal.