Jared Kushner. Jonathan Ernst/Reuters

President Donald Trump's son-in-law and senior adviser, Jared Kushner, denied in a statement Monday that he suggested setting up a "back channel" communication line to the Kremlin that would bypass US intelligence agencies and persist after Trump was inaugurated.

But Kushner acknowledged in the statement, which came ahead of a closed-door appearance before the Senate Intelligence Committee, that he asked Russia's ambassador to the US in December whether the Trump transition team could use Russia's embassy to communicate privately with Moscow about Syria.

The meeting with the ambassador, Sergey Kislyak, "occurred in Trump Tower, where we had our transition office, and lasted twenty [to] thirty minutes," Kushner wrote in an 11-page statement detailing his contacts with Russian nationals during the election and transition period.

"Lt. General Michael Flynn (Ret.), who became the President's National Security Advisor, also attended ... I stated our desire for a fresh start in relations."

Kushner said Kislyak, whose tenure in the US ended this past weekend, asked whether there was "a secure line in the transition office to conduct a conversation" about the US's Syria policy.

"General Flynn or I explained that there were no such lines," Kushner wrote. But he said he went on to ask whether the Russian Embassy "had an existing communications channel ... we could use where they would be comfortable transmitting the information they wanted to relay to General Flynn."

Kislyak said they didn't, according to Kushner, and "nothing else occurred."

"I did not suggest a 'secret back channel,'" he wrote. "I did not suggest an on-going secret form of communication for then or for when the administration took office. I did not raise the possibility of using the embassy or any other Russian facility for any purpose other than this one possible conversation in the transition period. We did not discuss sanctions."

Kushner's statement appears consistent with a Washington Post report published in May that said he had floated the possibility of setting up a secure line of communication between the Trump transition team and Russia — and having those talks take place in Russian diplomatic facilities in the US, essentially concealing their interactions from US government scrutiny.

According to The Post, Kislyak was "taken aback" by Kushner's request because it posed significant risks for both the Trump team and the Kremlin. But he passed along that request to Moscow anyway.

Kushner did not previously disclose the December meetings with Kislyak and the CEO of a Russian bank, Sergey Gorkov, on his security clearance form. He said in his statement that the form was submitted prematurely.

'A staggering lack of common sense'

Experts have said that if the Kushner-Kislyak meeting and reported discussion were an isolated incident, then it could be spun as normal back-channel communication arrangements among states.

But Kislyak and the Trump campaign interacted extensively, and Trump associates either kept those interactions secret from US officials or misrepresented them, as was the case with Flynn, who was forced to resign in February for similar reasons.

Scott Olson, a recently retired FBI agent who ran counterintelligence operations and spent more than 20 years at the bureau, told Business Insider in May that it was not unusual for low-level staffers to work between governments and bypass bureaucracy to exchange views and build consensus in advance of higher-level negotiations.

But what Kushner appears to have done is "substantially different, in two ways," he said.

"First, he is not seeking a back channel for a low-level staff exchange," Olson said. "He wants high-level direct-contact communication. This is extremely dangerous because it results in verbal (and therefore undocumented and unwitnessed) agreements, which are binding on governments. Free governments do not work this way. They can't. If they do, they are no longer free."

He added:

"Second, he asked to use a foreign government's communication facilities. This is way beyond a private server. This is doing US government diplomatic business over a foreign government's communication system. It's not an off-the-record conversation. It's a conversation recorded by the opposing party. This shows a staggering lack of understanding of the US and its place in the world. Actually, it shows a staggering lack of common sense. When he negotiates a business deal does he use the other guy's notes?"

It also struck many experts as odd that Flynn, Kushner, and Kislyak would want to conceal discussions about Syria from the US's national security and intelligence communities.

"Why in God's name would they want to conceal plans on Syria strategy from the US military?" asked Susan Hennessey, a former attorney for the National Security Agency. "Even accepting their Syria spin, what Kushner tried to do was blind the US government on incredibly important national security matters. That's not how it works. That's not the behavior of someone who recognizes America is still, at its core, a common endeavor."