WASHINGTON — The United States is stepping up digital incursions into Russia’s electric power grid in a warning to President Vladimir V. Putin and a demonstration of how the Trump administration is using new authorities to deploy cybertools more aggressively, current and former government officials said.

In interviews over the past three months, the officials described the previously unreported deployment of American computer code inside Russia’s grid and other targets as a classified companion to more publicly discussed action directed at Moscow’s disinformation and hacking units around the 2018 midterm elections.

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