The warning to Russia came four weeks before the November 8 election to pick a successor to the Democratic president
The United States will give a measured response to what it believes to be Russian interference in the US election process, including the hacking of Democratic Party computers, a White House spokesman said Tuesday.
"We obviously will ensure that our response is proportional," spokesman Josh Earnest told reporters traveling with President Barack Obama on Air Force One.
"It is unlikely that our response would be announced in advance," he added.
The warning to Russia came four weeks before the November 8 election to pick a successor to the Democratic president.
Last Friday, the Obama administration formally accused the Russian government of trying to "interfere" with the American election, and vowed to respond at an undisclosed time and place.
The assertion against Russia came with relations already frayed over NATO defenses and stalled efforts to end the bloody civil war in Syria.
Earnest highlighted the United States' capacity for responding to cyber attacks.
"The president has talked before about the significant capabilities that the US government has to both defend our systems in the United States but also carry out offensive operations in other countries," he said.
The US statement, issued Friday, said the American intelligence community "is confident that the Russian government directed the recent compromises of emails from US persons and institutions, including from US political organizations."
It also said the disclosures of allegedly hacked emails on WikiLeaks and other websites and by the online persona "Guccifer 2.0" were "consistent with the methods and motivations of Russian-directed efforts."
Hillary Clinton, the Democratic presidential nominee, has accused Russia of trying to tilt the presidential election in Republican rival Donald Trump's favor through a series of email hacks.
The Obama administration has appeared prudent about the way it responds to hacking and computer attacks, seeking to avoid an escalating cyber war.
The line sometimes is difficult to draw between traditional espionage -- which the United States also practices, and must thus tolerate -- and full-blown cyber assaults.
The Obama administration has repeatedly declared its right to respond with all the means at its disposal, and not only through technology measures.
After North Korea hacked Sony Pictures in 2014, Obama responded with economic sanctions against the regime.