WASHINGTON — President Barack Obama is promising that the U.S. will retaliate against Russia for its suspected meddling in America’s election process, an accusation the Kremlin has vehemently denied.

As the White House grew more bullish about suggesting President Vladimir Putin was personally involved, Obama said he’d spoken directly to Putin about his concerns about Russian meddling. He said whenever a foreign government tries to interfere in U.S. elections, the nation must take action “and we will at a time and place of our own choosing.”

“We have been working hard to make sure that what we do is proportional, that what we do is meaningful,” Obama said in an NPR News interview airing Friday.

Obama’s remarks were the clearest indication that whatever response the U.S. is planning, it hasn’t happened yet. The White House has insisted for months that when the U.S. did retaliate, it might not be made public, a position that has created uncertainty about the strength and timing of any response.

Obama was expected to face questions about the hacking and his response during a news conference at the White House on Friday afternoon.

White House officials said it was “fact” that Russian hacking helped Donald Trump’s campaign against Democratic presidential nominee Hillary Clinton. White House press secretary Josh Earnest on Thursday also assailed Trump himself over his refusal to acknowledge the hacking and his attacks on the U.S. intelligence community.

The tough talk from the White House fell flat in Moscow, where Putin spokesman Dmitry Peskov called the accusations baseless and inappropriate.

“They should either stop talking about that, or produce some proof at last,” Peskov told reporters Friday. “Otherwise it all begins to look unseemly.”

There has been no specific, persuasive evidence shared publicly about the extent of Putin’s role or knowledge of the hackings. That lack of proof undercuts Democrats’ strategy to portray Putin’s involvement as irrefutable evidence of a directed Russian government plot to undermine America’s democratic system.

But the White House pointed to a U.S. intelligence assessment released publicly in October that asserted “only Russia’s senior-most officials could have authorized these activities.” And Obama’s deputy national security adviser, Ben Rhodes, connected the dots further, saying Thursday Putin was responsible for the Russian government’s actions.

“I don’t think things happen in the Russian government of this consequence without Vladimir Putin knowing about it,” he told MSNBC.

Trump struck back Friday morning, with a Twitter post mockingly asking “are we talking about the same cyberattack” in which embarrassing information about the Democratic National Committee was also revealed. His tweet invoked emailed stolen from Hillary Clinton’s campaign chairman and later released publicly in hacking that has been linked to Russia.