Russia’s central bank said it will suspend sales of rubles to purchase foreign exchange through the end of September in an effort to steady the currency, helping pull it back from the lowest level in two years.

The move was the most dramatic official step yet to stem the currency’s declines, which have picked up in recent days amid growing fears of U.S. sanctions. Alarm over the impact of possible new restrictions being discussed in Washington has spread beyond financial markets, with the government saying Wednesday it will have to trim economic growth forecasts for this year because of the turmoil and surging outflows of capital.

The central bank’s announcement was the first time the regulator has given a time frame for staying out of the market since the foreign-exchange-buying program began in early 2017.

“This decision was made in order to increase the predictability of monetary authorities’ actions and to reduce volatility on financial markets,” the central bank said in a statement Thursday. It said the decision to resume foreign-exchange purchases “would be made depending on the situation on financial markets over the course of September.”

Reserve buildup

The central bank sells rubles to buy foreign currency for the Finance Ministry to build up reserves under a fiscal rule aimed at insulating the economy from volatility in oil prices. The regulator had suspended its transactions for six days earlier this month when the ruble was falling, but resumed them on Aug. 17 in larger volumes. On Tuesday, the central bank sold 20.1 billion rubles ($293 million). The Finance Ministry said the pause wouldn’t affect its accumulation of reserves under the fiscal rule.