In this Feb. 14, 2018 photo, Treasury Secretary Steven Mnuchin testifies before the Senate Finance Committee on Capitol Hill in Washington. The Trump administration accused Russia on Thursday of a concerted, ongoing operation to hack and spy on the U.S. energy grid and other critical infrastructure. (AP Photo/Susan Walsh)
In this Feb. 14, 2018 photo, Treasury Secretary Steven Mnuchin testifies before the Senate Finance Committee on Capitol Hill in Washington. The Trump administration accused Russia on Thursday of a concerted, ongoing operation to hack and spy on the U.S. energy grid and other critical infrastructure. (AP Photo/Susan Walsh)

Washington — The Trump administration on Thursday took its strongest action to date to punish Moscow for interfering in the 2016 election, imposing fresh financial sanctions on Russian government hackers and spy agencies.

The administration also formally backed Britain’s claims that Moscow is almost certainly to blame for a chemical toxin attack against a former Russian spy living in England who was found comatose along with his daughter earlier this month.

The sanctions were the first such actions taken under legislation passed nearly unanimously last year by Congress and follow months of criticism that the White House has been slow to counter Russian aggression. But the steps taken on Thursday fell well short of the full penalties Congress authorized and focused on a narrow list of targets rather than the broader range of individuals and entities believed to have played a role in Russia’s efforts to interfere in the election.

In both cases, pressure from Congress and allies helped nudge the White House toward a stronger response. Republicans have joined Democrats in urging the administration to penalize Russia more strongly, while suggesting that President Donald Trump set aside concerns about examining the election interference that he initially dismissed as a “hoax.”

Lawmakers have been telling the White House for months that Russia will surely try to expand its interference in the upcoming congressional midterm elections.

Sen. Robert Menendez, D-N.J., the senior Democrat on the Senate Foreign Relations Committee, called the sanctions announcement a “long overdue response” but noted that the administration has failed to implement six other mandatory provisions of the law enacted last year, including penalties affecting Russian defense and other industries.

“I expect to see additional sanctions in short order against specific Russian entities responsible for undermining our democracy,” he said in a statement. “The longer we wait, we know the Russian government will continue to shift resources to other propaganda factories that spew disinformation and lies.”

Menendez also said the Obama administration had already sanctioned many of those on the Trump administration’s list.

The White House also faced criticism that it muddied its response to the election interference by saying the penalties also were in response to Russia’s cyberattack last year against Ukraine and other countries, which officials have characterized as “the most destructive and costly” in history.

White House press secretary Sarah Huckabee Sanders would not say on Thursday whether the administration considers Russia a friend or foe, instead turning the onus on Moscow.

“Russia’s going to have to make that determination. They’re going to have to decide whether or not they want to be a good actor or a bad actor,” Sanders said. “I think you can see from the actions that we’ve taken up until this point, we’re going to be tough on Russia until they decide to change their behavior.”

The penalties on 19 Russians were expected after a top administration official had pledged, under critical congressional questioning last week, that the administration would act within a week to use the mandate Congress had approved last summer.

The penalties also partly mirror the investigation pursued by Special Counsel Robert Mueller.

Thursday’s list included 13 people who had been indicted by Mueller, meaning they were already subject to legal jeopardy that is more serious than the sanctions.

A senior administration official said the timing of Thursday’s announcements were due to the completion of months of work to prepare the sanctions and the collective desire among the United States and allies to respond quickly to the “atrocious hostile act” against the former spy in England.

Separately on Thursday, the Department of Homeland Security and the FBI issued a report describing sophisticated Russian government attempts to target American and European power plants, nuclear facilities, airports and other critical infrastructure for cyberattacks.

It characterized the activity as “a multi-stage intrusion campaign by Russian government cyber actors,” while describing in minute detail how the digital assailants “staged malware, conducted spear phishing, and gained remote access into energy sector networks.”

The report indicated that the attackers appear to have penetrated the networks of key industrial sites in the United States and Europe, suggesting they could shut down or disrupt those systems with relative ease.

It repeated the key findings shared by the agencies in July, when they said that there was no evidence the hackers penetrated or damaged the core systems that control operations at the infrastructure sites and that public safety was never in jeopardy.

While the administration joined Britain and other allies on Thursday in condemning Russia for the attack in Salisbury, England, that left the former spy and his daughter comatose, it has not said whether it plans any retaliation against Moscow. Britain has expelled Russian diplomats in protest.

After days in which the administration had not fully affixed blame over the incident, U.N. Ambassador Nikki Haley blasted Russia during a Security Council session on Wednesday. Her remarks were approved by White House officials but went further than other officials had gone at that point.

“The United States believes that Russia is responsible for the attack on two people in the United Kingdom using a military-grade nerve agent,” Haley said, accusing Russia of violating international law.

“If we don’t take immediate concrete measures to address this now, Salisbury will not be the last place we see chemical weapons used,” Haley said. “They could be used here in New York or in cities of any country that sits on this council.”