At 0755 GMT, the rouble was 0.16 percent weaker against the dollar at 56.97 and had lost 0.06 percent to trade at 70.17 versus the euro.

British Prime Minister Theresa May said it was "highly likely" that Moscow was responsible for the poisoning in England of Russian former double agent Sergei Skripal and his daughter using a military-grade nerve agent.

London has given Russia until the end of Tuesday to explain its use and US Secretary of State Rex Tillerson already said the United States had "full confidence" in Britain's assessment that Russia was likely responsible for poisoning.

"In particular, the next calls for sanctions - this time, from the United Kingdom - can bring undesirable volatility (for the rouble)," analysts of Rosbank, a subsidiary of Societe Generale, said in a note.

Rosbank also said that despite new geopolitical threats there were several reasons for the pressure on the rouble, including a general fall in the emerging market currencies and a drop in oil prices.

Oil prices slightly fell on Tuesday as the inexorable rise in US crude output weighed on markets.

Brent crude oil, a global benchmark for Russia's main export, was up 0.31 percent at $64.75 a barrel.

The market awaits the US inflation data later in the day which could offer clues on the pace of interest rate rises this year.

Russian stock indexes were down.

The dollar-denominated RTS index was down 0.5 percent to 1,277 points. The rouble-based MOEX Russian index was 0.4 percent lower at 2,308 points.