At 0759 GMT, the rouble was 2.6% weaker against the dollar at 56.68, its weakest point since June 20. The unit had lost 1.4% to trade at 58.58 versus the euro.
The rouble's recent slump from more than seven-year highs hit last Wednesday is just a correction on the market, said Alor Broker in a note.
"It is too early to talk about a break in the rouble's strengthening trend," Alor Broker analysts wrote. "Russia's balance of payments will continue to remain very strong, importers will not recover their positions quickly.
"Only by introducing a new budget rule can the situation on Moscow Exchange's currency market change radically."
The rouble is still the world's best-performing currency https://emea1.apps.cp.thomsonreuters.com/Apps/NewsServices/mediaProxy?apiKey=6d416f26-7b24-4f31-beb6-1b5aa0f3fafb&url=http%3A%2F%2Ffingfx.thomsonreuters.com%2Fgfx%2Frngs%2FGLOBAL-CURRENCIES-PERFORMANCE%2F0100301V041%2Findex.html this year, boosted by measures - including restrictions on Russian households withdrawing foreign currency savings - taken to shield Russia's financial system from Western sanctions imposed after Moscow sent troops into Ukraine on Feb. 24 in what it calls a "special military operation".
Proceeds from commodity exports and a sharp drop in imports are further factors behind the currency's gains. But the rouble has now lost the support of last week's tax-driven dollar and euro sales.
Expectations of the imminent launch of currency interventions, which Finance Minister Anton Siluanov said Russia could turn to as it tries keep a lid on the rouble's strengthening, may continue to pull support from the rouble on Tuesday, said Promsvyazbank analysts.
Potanin, the largest shareholder at Nornickel, is ready to discuss a possible merger of the mining giant with Rusal amid Western sanctions, he said in an interview with RBC TV.
Rusal's Moscow-listed shares leapt more than 20% before settling around 10% higher. Shares in En+, Rusal's majority shareholder, were 10.5% higher in Moscow. Nornickel shares fell 2.1%.
Russian stock indexes were lower.
The dollar-denominated RTS index was down 2% to 1,224.0 points. The rouble-based MOEX Russian index was 0.1% lower at 2,202.0 points.
(Reporting by Reuters)