At a meeting of the city's emergency situations committee "it was decided to block the flow of the Kazakevich" channel, located at the confluence of the Amur and Ussuri Rivers, 60 kilometres (37 miles) upstream from Khabarovsk, the ministry said in a written statement.

"This measure would prevent pollutants reaching the Amur" in the stretch that runs beside Khabarovsk, the statement said.

The Amur River splits into numerous branches around the Amur-Ussuri confluence, and Khabarovsk is fed mainly from waters that must pass through the Kazakevich channel before those branches merge again downstream from the city.

Earlier a Chinese diplomat held talks with officials in Khabarovsk and promised China would provide Russia with testing equipment and charcoal to help alleviate the threat of the chemical slick.

The slick, made up mainly of the carcinogen benzene and nitrobenzene, was reported to have extended in length to around 100 kilometres (62 miles) as it moved down the Songhua River in China towards Russia.

China "is doing everything to neutralise the consequences of this major disaster" Fan Syanzhun, the Chinese consul in Khabarovsk, was quoted by the ITAR-TASS news agency as saying.

China's government "is paying great attention to cooperation with the Russian side aimed at minimising the threat arising from the emergency situation in Khabarovsk region" and Russia's Jewish Autonomous Province, which lies upstream from Khabarovsk, he said.

Authorities in Khabarovsk have been stockpiling supplies of fresh water in case the main supply of the city of about 600,000 people become polluted.

Harbin, the capital of China's Heilongjiang province, suffered a five-day water shutdown as the spill entered that city last month.

Russia's Emergency Situations Ministry earlier estimated the slick would reach Nizhneleninsk, in the Jewish Autonomous Province, on December 6-8, followed by Khabarovsk on December 9-11.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.