Sanktioner mot Ryssland.

Sanctions may have knocked as much as 6 percent off Russia’s economy over the past four years and the drag isn’t likely to go away anytime soon.

A new study by Bloomberg Economics has found that the economy of the world’s biggest energy exporter is more than 10 percent smaller compared with what might have been expected at the end of 2013, before the Crimea crisis triggered wave after wave of restrictions by the U.S. and EU. While some of the blame falls on the slump in oil prices, sanctions are the bigger culprit.

“The underperformance has been much bigger than crude alone can explain,” wrote Scott Johnson, an analyst at Bloomberg Economics in London. “Part of the gap is likely to reflect the enduring impact of sanctions both imposed and threatened over the last five years.”

Congress isn’t expected to pass legislation ordering new U.S. sanctions on Russia before the end of the year, as lawmakers focus instead on government spending measures, judicial nominations and a farm bill, key senators said.

A bipartisan group of senators moved swiftly over the summer to assemble new proposals for Russia sanctions following President Donald Trump’s summit with Russian President Vladimir Putin in Helsinki. But as Congress enters the so-called lame duck period before newly elected lawmakers take office in January, time is running short for action on the bills.

The U.S. Treasury Department told Congress on Wednesday it will remove sanctions imposed on three Russian companies tied to an oligarch.

The companies—aluminum giant United Co. Rusal PLC, its parent EN+ Group PLC and JSC EuroSibEnergo, a Russian energy company—were put on the U.S. sanctions list in April because of their ownership or control by Russian oligarch Oleg Deripaska.

Mr. Deripaska remains under sanctions, but the companies agreed to a sweeping deal centered on severing his ties with them that will result in their removal from the blacklist, the Treasury said.

The removals, expected to take place in 30 days, are based on a change in factual circumstances “in line with longstanding U.S. sanctions precedent” that “is not intended to significantly alter U.S. foreign policy,” the Treasury said in a letter to Congress.

The removals come as the U.S. imposed fresh sanctions against 15 Russian agents, including a former Russian intelligence officer who the U.S. said reports to Mr. Deripaska and led business negotiations on his behalf.