Alrosa competes with Anglo American De Beers, the biggest seller of rough diamonds by value.

Alrosa's sales of rough and polished diamonds totalled $504.5 million in January 2018 due to good retail sales and high polished diamond prices.

"(The figure in January) will certainly be lower than in January a year ago," Sergey Ivanov was quoted as saying on the sidelines of the World Economic Forum in Davos, Switzerland.

An annual period of weaker demand in the rough diamond sector seems to be shifting from the summer months, which showed abnormally high demand in 2018, as demand in January had been rather low, he added.

Ivanov expects the demand for small-sized diamonds to recover in March or April amid declining rough diamond stockpile in India's diamond polishing sector, Interfax said.

The company currently plans to produce and sell 38 million carats of rough diamonds in 2019, he added.

In 2018, it produced 36.6 million carats and sold over 38 million carats. Its sales were larger than production as Alrosa used part of its stockpile. This stood at 17 million carats at the start of 2019, Ivanov was quoted as saying.

(Reporting by Polina Devitt; editing by Alexandra Hudson)