The rouble was 0.1 percent weaker at 62.55 versus the dollar as of 0751 GMT and firmed 0.1 percent to 73.09 versus the euro.

According to a Reuters survey of analysts, the rouble is likely to trade within a range of 61-64 versus the dollar this month but there is a risk it could weaken beyond that.

August has a reputation for being bad for the rouble. Data shows that, since 1991, it has usually weakened during the month, which has been associated with major market-negative events including a state default in 1998 and war with Georgia in 2008.

Denis Davydov, economist at Nordea bank in Moscow, said he did not expect the currency to sustain substantial losses this August. "Even though August is traditionally viewed as the worst month for the rouble, we do not tend to dramatise this," he said.

Sanctions against Russia are currently in the spotlight after the US Treasury Department extended the deadline for investors to divest holdings in Russian firms EN+, GAZ Group and Rusal.

The companies were hit in April by sanctions against Russian billionaire Oleg Deripaska, who has holdings in all three, in response to what the US Treasury termed "malign activities" by Russia.

Shares in Rusal slipped 0.8 percent after the United States said investors now had until Oct. 23 to divest their shares in the company versus a previous deadline of Aug. 5.

The dollar-denominated RTS index was down 0.3 percent to 1,169.0 points and its rouble-based peer MOEX was steady at 2,321.0.