The White House fumed Wednesday about an embarrassing leak regarding Donald Trump's shock decision to congratulate Russia's Vladimir Putin on his re-election, as lawmakers blasted him for feting the strongman's landslide win.
Trump shunned the advice of some aides in making the call in the first place, after Putin sailed to a fourth term in a vote plagued by evidence of ballot stuffing, media censorship and the jailing of political opponents.
But the controversy was compounded as it emerged the president's prepared notes for the call had specifically warned him "DO NOT CONGRATULATE" -- with a hunt now underway for the person who leaked the document.
The row erupted as lawmakers heard that Russia -- slapped with US sanctions over its meddling in the 2016 election -- remains a menace as the country gears up for congressional polls in November.
"The threat of interference remains," Homeland Security Secretary Kirstjen Nielsen told a hearing of the Senate Intelligence Committee on election security.
"We recognize that the 2018 midterm, and future elections, are clearly potential targets for Russian hacking attempts," she said.
Democratic Senator Mark Warner told the hearing it was "clear that 2016 will not be the last attempt" to meddle by Russia, calling Trump out for his failure -- once again -- to tackle the subject with Putin.
"The fact that the president did not even bring up the topic of our election security when he called Vladimir Putin to congratulate him on his 'victory' in a pre-cooked election, is extremely troubling."
The Washington Post and others reported that aides explicitly advised Trump not to congratulate the Russian president, and instead urged him to condemn the poisoning of a former Russian spy in Britain.
According to accounts from the White House and the Kremlin, Trump did neither.
The leak of such sensitive information about Oval Office deliberations points to deep frustration within the White House about the president's ad-hoc approach and disregard for the advice of his inner circle.
Only individuals at the very highest levels of the administration would have known about the details of the call.
Officials, speaking on condition of anonymity, told AFP that a hunt for the leaker was underway.
One suggested the documents prepared for the call may have been classified, making unauthorized disclosure a crime.
The furor in the White House over the leak broke out even as Nielsen, Trump's top domestic security official, sounded a fresh warning about the threat posed by Russia.
"It needs to be very clear that there are consequences for countries that meddle in our affairs."
Warner said Moscow's threat has grown larger than in 2016.
"There are signs that the Kremlin is becoming more brazen. As we saw recently, the Putin regime was behind an assassination attempt on European soil with a prohibited military-grade nerve agent. This is not the action of a regime that is being successfully deterred."
He echoed the criticism of Trump's call by Republican Senator John McCain, who warned on Wednesday that "an American president does not lead the free world by congratulating dictators on winning sham elections."
Allies, most notably in Britain, were furious about Trump's apparent lack of solidarity after double agent Sergei Skripal was poisoned in a small English town.
The White House waited for days before condemning the attack, which London has pinned squarely on the Kremlin and Moscow has denied.
Also facing mounting domestic pressure over his unwillingness to confront Putin, the White House said Wednesday Trump agreed in a call with French President Emmanuel Macron "on the need to take action to hold Russia accountable" over the attack.
For critics, Trump's call offered Putin legitimacy while giving him a wedge to drive between Western allies and within the White House itself.
But Republicans also lined up behind the president in anger about the latest leak from the White House.
"I don't like that he did it, but you know what I like even less? That there is somebody close to him leaking this stuff out. If you don't like the guy, quit!" said Republican Senator Marco Rubio.