(Adds Belarus comments on transit, details)
By Gleb Gorodyankin, Olesya Astakhova and Vladimir Soldatkin
MOSCOW, Jan 15 (Reuters) - Belarus has started planned maintenance on the Druzhba oil pipeline, the main transit route for Russian oil exports to Europe, resulting in reduced oil supplies to Poland, a source familiar with the plan told Reuters.
Both Belarus and Russia, which are locked in a dispute over a new oil contract, said the maintenance was planned in advance.
The energy spat is part of a wider row between Moscow and Minsk as the Kremlin seeks to cement its influence over its neighbour, which is seen as a buffer between the West and Russia.
Moscow suspended oil supplies to Belarus from Jan. 1, but partially restored them on Jan. 4. Two Russian oil firms, controlled by tycoon Mikhail Gutseriyev, supply Belarus with oil essential to minimum operations at its two refineries.
The source at pipeline company Gomeltransneft Druzhba said the maintenance started on Jan. 14 and would last until Jan. 17 at the Mozyr-Gomel 3 part of the Druzhba pipeline, and oil shipments to Poland were reduced to 70,000 tonnes per day, or half of the usual volumes, for that period.
An industry source said that on Jan.1-14 the oil supplies had been increased from usual levels to 1.9 million tonnes compared with an expected 3.2 million tonnes for the whole of January.
Druzhba splits into two routes in Belarus - a northern leg to Poland and Germany, and a southern leg to Ukraine, the Czech Republic, Hungary and Slovakia.
The source said the maintenance was to replace two small sections of the pipeline and that Russian oil pipeline monopoly Transneft was given a heads-up notice about the works in December.
Separately on Wednesday, Gomeltransneft Druzhba said Minsk planned to conduct maintenance on the Druzhba oil pipeline on a monthly basis.
The maintenance will cause a drop in pressure in the pipeline and a partial disruption to pumping, it said.
Later, Belarus news agency Belta reported - citing Gomeltransneft - that the maintenance won’t affect the transit and that the repair work was agreed with Russia.
Transneft chief executive Nikolai Tokarev on Wednesday ruled out a halt to Russian oil transit via Belarus, but said it was able to divert oil flows if needed. (Reporting by Anton Kolodyazhnyy, Gleb Gorodyankin, Olesya Astakhova, Vladimir Soldatkin and Maria Grabar in Moscow; Andrei Makhovsky in Minsk; Writing by Anastasia Teterevleva; Editing by Mark Potter/Emelia Sithole-Matarise)