In recent weeks, President Donald Trump’s national security advisers have pushed for more sanctions after a series of alleged moves by Russia, including the poisoning of a former Russian spy in England, interference in the US 2016 elections and a cyberattack described as the most destructive and costly in history.

Officials spoke about the sanctions on the condition of anonymity because they were not authorised to discuss pending actions.

The push for more sanctions came as three buses believed to be carrying expelled diplomats departed from the US embassy in Moscow.

Russia last week ordered 60 American diplomats to leave the country by Thursday, in retaliation for the United States expelling the same number of Russians.

The moves were part of a deepening dispute over the nerve-agent poisoning in Britain of Russian former double-agent Sergei Skripal and his daughter.

Britain alleges Russian involvement, which Moscow vehemently denies.

On Tuesday night, outgoing national security adviser H.R. McMaster called on the United States to take a tougher line against Moscow, saying: “We have failed to impose sufficient costs”.

The remark came hours after Trump said in a White House news conference that “nobody has been tougher on Russia than I have”.

Russian officials, meanwhile, have expressed exasperation with the United States. Moscow’s ambassador to the United States, Anatoly Antonov, said the “atmosphere in Washington is poison”.

“It’s a toxic atmosphere,” he told NBC News.

The United States is expected to target individuals on a list of influential Russian political and business leaders that the Treasury Department released in January, officials said.

The United States could also impose sanctions based on authorities Congress granted to target anyone conducting significant business with Russian intelligence and defence sectors.

“If they do something tough like this, it may go some distance in reassuring angry members of Congress and the public who are looking at the midterms and wondering if this administration is focused on the Russian threat and taking moves to address it,” said Liz Rosenberg, a former Treasury official who is at the Centre for a New American Security.

White House and State Department spokesmen declined to comment.

The pending Treasury move comes as the Trump administration takes an increasingly tough posture toward Moscow at the urging of his senior aides and top US allies.

There has been a flurry of tit-for-tat diplomatic expulsions since the March 4 poisoning on UK soil of Skripal, which Britain says was carried out with a military-grade nerve agent developed by the Soviet Union.

The former double agent, who defected to Britain, was found slumped on a park bench in the English town of Salisbury alongside his daughter Yulia who was also critically injured.

London has said it is “highly likely” Moscow was behind the botched assassination, a charge the Kremlin has angrily denied.

Relations between Moscow and the West have since plummeted to a new lows.

More than 150 Russian diplomats were ordered out of the US, EU members, Nato countries and other nations as punishment, a move that was met in kind by Russia.

The Washington Post, Associated Press