A Russian official on Tuesday warned that the building of the country's longest oil pipeline from Eastern Siberia to the Asian-Pacific region may be suspended, the Interfax news agency reported.

The second phase of the Eastern Siberia-Pacific Ocean (ESPO) pipeline may be put off by three or four years due to lack of reserves, the Interfax said, citing Sergei Fedorov, director of the Natural Resource Ministry's state geological policy department.

"Due to a delay in reserves growth, the building of the second phase of the pipeline, which means, an expansion to 80 million tons of oil per year, may be postponed by three to four years," he said.

The ESPO pipeline will run from Taishet in Eastern Siberia to Nakhodka near the Sea of Japan along a 4,000 kilometers route, to give Russia access to countries of the Asian-Pacific region. Its annual capacity will be 80 million tons.

Oil will be exported from a port near Nakhodka to Japan, South Korea and other countries. Meanwhile, an extension of the pipeline will be built from Skovorodino to China.

However, the currently two recoverable oil fields in Eastern Siberia recorded a reserve of 700 million tons and can only feed the pipeline 30 million tons of oil per year, Fedorov said.

The first phase of the project, which kicked off last April and some 800 kilometers pipeline have been laid, bears a capacity of 30 million tons of oil from Taishet to Skovorodino. It was expected to be completed in late 2008.

Initially the first phase pipeline will pump crude from West Siberia along the existing Omsk-Irkutsk pipeline that will join the new project in Taishet. In future hydrocarbons from East Siberia and Yakutia will be added.

Fedorov called for more budget to explore oil in Eastern Siberia, which were estimated at one billion rubles (about 38.5 million U.S. dollars) per year.

The project operator Transneft has planned to spend 198.7 billion rubles for the ESPO construction in 2007, which is some 130 percent more than that in 2006. Some 1,250 kilometers of the pipeline were expected to be laid in 2007, the Interfax reported.

Transneft Vice President Sergei Grigoriev said that the company has no concrete timetable for the second phase.

"A decision on the start of construction of the second phase, which should be made by the government, will depend on the pace of development in Eastern Siberia," he said.