Uzbekistan Wednesday warned world powers of a looming environmental disaster from Tajikistan's plan to build a huge hydro-electric dam, in a new show of tensions from the ex-Soviet neighbours.

Tashkent also accused Tajikistan's main aluminium plant, the largest in Central Asia and located near Uzbekistan's southern border, of causing increased fluorine-related diseases among the population and millions of dollars damage to its agriculture.

"Thoughtless management of transborder rivers, construction of environmentally harmful industrial projects made during the second half of the last century put our region on the verge of environmental disaster," Uzbek President Islam Karimov said in a message to an international conference that opened in Tashkent.

The conference gathered more than 100 environmental experts from over 30 countries, including the US and European Union members.

The issues on the agenda highlights the increasingly tense relations between the two Central Asian states, which have been at odds on a number of issues for almost two decades since the collapse of the Soviet Union.

Mountainous Tajikistan has pledged to move ahead unilaterally in the construction of the Rogun dam, which was first conceived as a gigantic Soviet hydro-electric power project.

Tajikistan, the poorest of the ex-Soviet republics of Central Asia, sees Rogun as a means of solving its chronic energy shortages while at the same time allowing it to become a net exporter of electricity.

Uzbekistan warns that Rogun dam is located in a highly seismic zone and can put millions of lives in downstream countries in danger if natural or technical disasters occur.

Tashkent also fears the dam will damage its vital cotton industry, which depends on water which flows in from Tajikistan and Kyrgyzstan, and negatively impact millions of Uzbeks living downstream.

"This is a political issue. There is a need for state-level discussions involving all of the countries in the region," a top international official attending the conference told AFP, asking not to be named.