The host of the summit, Kazakh President Nursultan Nazarbayev, had presented his counterparts from Uzbekistan, Tajikistan, Kyrgyzstan and Turkmenistan with a joint declaration on resolving the water issues of their arid region.

But he was visibly embarrassed when Tajik President Emomali Rakhmon publicly refused to sign the statement, which Nazarbayev had offered as a compromise.

Rakhmon's refusal came in an earthy outburst after he was apparently angered by other leaders' assertions that water-supplying countries such as Tajikistan were responsible for chronic shortages.

"No, I do not agree and I will not sign it. We were not supposed to talk about (water supplies)," Rakhmon barked across a large table, in an exchange that was visible to journalists watching on closed-circuit television.

The leaders later signed a compromise statement on the condition that it avoid the controversial issue of water-sharing and focus only on the official topic of the summit -- the decline of the Aral Sea.

The text of the statement was not immediately shared with journalists.

Underpinning the clash at the summit were long-running disputes over the distribution of water, a precious commodity in arid Central Asia.

Most of the region's water supply originates in mountainous Kyrgyzstan and Tajikistan before travelling onward to their parched neighbours.

The two ex-Soviet states suffer from electricity shortages and have proposed building up their hydro-electric generation capacity as a means of becoming energy-independent.

Meanwhile downstream countries complain they do not receive their fair share for irrigation projects such as Uzbekistan's lucrative cotton fields, and have responded by periodically cutting off energy to their poorer neighbours.

Tuesday's summit was the first meeting of the leaders of all five countries under the auspices of the International Fund to Save the Aral Sea since 2003.

The decline of the Aral Sea has become a rallying cry for environmentalists concerned over unsustainable growth amid limited water resources.

A body of water between Kazakhstan and Uzbekistan, the Aral Sea was once the world's fourth largest inland lake, but it has been receding for decades as its tributaries have been starved by massive Soviet-era irrigation projects.