The Russian rouble hovered around 99.5 to the dollar on Thursday, struggling to pull away from the 100 threshold it breached earlier this week, hurt by reduced foreign currency supply from exporters early in the month.

At 0818 GMT, the rouble was unchanged against the dollar at 99.60 and steady at 104.72 versus the euro . It had firmed 0.2% against the yuan to 13.61.

The rouble has lost support of a favourable month-end tax period that usually sees exporters convert FX revenues to meet local liabilities.

Brent crude oil, a global benchmark for Russia’s main export, was up 0.2% at $86.02 a barrel.

Russia’s oil and gas revenues rose in September, boosted by higher oil prices and as Moscow finds new export destinations after Western price caps and an embargo on seaborne oil exports squeezed energy revenues.

Energy revenues are likely to continue recovering in October due to tax changes and high commodity prices.

The finance ministry’s expected rise in tax revenues from the sector in October could give the rouble some strong support, said Alor Broker’s Alexei Antonov, as oil companies would be forced to increase their sales of foreign currency export earnings.

“But this will happen either in the second half of the month, or when the exchange rate goes above 100 roubles per dollar,” Antonov said.

Russian stock indexes were lower.

The dollar-denominated RTS index was down 0.3% to 988.4 points. The rouble-based MOEX Russian index was 0.3% lower at 3,123.7 points.