White House Senior Advisor Jared Kushner attends a swearing in ceremony for U.S. Ambassador to Israel David Friedman at the Executive office in Washington, U.S., March 29, 2017. REUTERS/Carlos Barria

On Friday, The Washington Post broke a bombshell report that President Trump's senior adviser and son-in-law Jared Kushner proposed setting up a back-channel of communication between Trump and Moscow using Russian facilities.

Over the next two days, the president's staff took to the airwaves to downplay concerns about the gravity of the situation.

On Saturday, national security adviser H.R. McMaster told reporters that he "would not be concerned about a back-channel" between Trump and the Kremlin.

"We have back-channel communications with a number of countries. So, generally speaking, about back-channel communications, what that allows you to do is to communicate in a discreet manner," McMaster said.

On Sunday, Department of Homeland Security secretary John Kelly told NBC's Chuck Todd that he was not bothered by the revelations either.

Kushner's "number one interest, really, is the nation. So you know there's a lot of different ways to communicate, back-channel, publicly with other countries," Kelly said. "I don't see any big issue here relative to Jared."

But experts say those rebuttals are skirting around one of the most serious concerns raised by the report: the specific request to use Russian gear to establish a line of communication.

"The idea of using Russian facilities to skirt Russian surveillance in the US would either be a serious attempt to hide something or the actions of a young amateur," Clint Watts, a former FBI agent and fellow at the Foreign Policy Research Institute, told The Atlantic.

"Contacts between a transition team and foreign diplomats is indeed entirely normal," said Eliot Cohen, a professor at Johns Hopkins University's School of Advanced International Studies and a former State Department official. "What is not normal, though, is asking a hostile government to provide secure comms to avoid FBI/NSA surveillance in order to do what, precisely."

Colin Kahl, a professor at Georgetown and former national security adviser to Joe Biden, echoed that assessment.

"A private citizen using secure comms of a hostile power to undermine US policy undetected is not good or normal," Kahl said on Twitter.

U.S. President Donald Trump gives a thumbs-up as he and White House Senior Advisor Jared Kushner depart the White House in Washington, U.S., March 15, 2017. REUTERS/Kevin Lamarque

The Trump administration's attempt to characterize the Kushner-Russia controversy as an acceptable form of back-channel communications is "infuriating," Glenn Carle, a CIA veteran and former spy, told Business Insider.

The establishment of a back-channel is "a sanctioned, appropriate kind of behavior done by the government in order to avoid notice. There is a place for a back-channel, but this wasn't that" Carle said. "This wasn't done by the government. It was done through the Russians."

According to the Post's report, Kushner asked Russian ambassador Sergey Kislyak in early December about setting up a line of communication between Trump and Moscow.

Trump had won the election by then, but he hadn't taken office yet. Kislyak was reportedly "taken aback" by Kushner's request, given the security risks that could arise when Americans use Russian communications gear at the country's embassy or consulate in the US.

Kislyak "can’t really believe, why would they want to do this? Why are they asking for this? It seems strange to him," The Washington Post's Greg Miller told PBS in an interview after the story broke.

'It's infuriating and punishable, and it is a crime'

Back-channel communications can be "legitimate and useful," said Bob Deitz, a veteran of the NSA and CIA who worked under former presidents Bush and Clinton. But "the principle problem is where [Kushner] proposed to have these communications," Deitz told Business Insider. "One just does not have back-channel communications in the switch room of a rival."

"For employee-security rules, the US intelligence community treats visiting a foreign embassy like visiting a foreign country," Susan Hennessey, a fellow at the Brookings Institution and former general counsel at the National Security Agency, told The Atlantic. "Many of the most significant examples of US espionage all occurred through foreign embassies."

And given the context surrounding Kushner's reported request, it's "just not possible" that this was an attempt to create a back-channel, Carle said. "If this were a one-off action by someone who's clueless or even willful, that's one thing. But this is the primary counselor to the president who has clearly had multiple communications with Russians that have not been sanctioned, not been announced," Carle said.

The "most alarming" aspect of this relates to the "dozens of hidden contacts with known Russian intelligence officers" that a number of Trump associates were found to have concealed, he added.

"It just goes on and on. All of that adds up to, not a back-channel, but to acting on behalf of a foreign power. It's infuriating and punishable, and it is a crime."

FBI Director James Comey listens before a meeting of the Attorney General's Organized Crime Council and Organized Crime Drug Enforcement Task Forces (OCDETF) Executive Committee to discuss implementation of the President's Executive Order 13773, at the Department of Justice, Tuesday, April 18, 2017, in Washington. Alex Brandon/AP

The White House has been besieged in recent days by a slew of negative news stories that have raised questions about the president's and his associates' ties to Russia. After Trump abruptly fired FBI director James Comey earlier this month, he told NBC's Lester Holt that "this Russia thing" had been a factor in his decision.

The week after, The Washington Post, citing officials familiar with the matter, reported that Trump disclosed highly classified information to Lavrov and Kislyak during their Oval Office meeting.

The following day, The New York Times broke news of a memo that officials said Comey wrote about a February meeting he had with Trump in the Oval Office. According to the memo, Trump asked Comey to drop the FBI investigation into former national security adviser Michael Flynn.

The next day, The Times reported that Flynn had informed the Trump transition team that he was under FBI investigation on January 4. According to The Times, Flynn told transition team member Don McGahn, who now serves as White House counsel, about the investigation. Flynn did not resign until over a month later, after The Washington Post reported that former acting attorney general Sally Yates had warned the White House in January that Flynn could be vulnerable to Russian blackmail.

Following those developments, deputy attorney general Rod Rosenstein appointed former FBI director Robert Mueller as a special prosecutor in charge of the FBI's Russia probe.

Later, it emerged that Trump told Russian officials during an Oval Office meeting that Comey was "a real nut job" and that firing him had taken "great pressure" off him.

But the most recent report involving Kushner is by far the most concerning, Carle said.

"What happened with Comey was shocking and outrageous, no doubt. That may have been an obstruction of justice. But this would be espionage," he said. "And espionage is worse than obstruction of justice."