The former Russian ambassador to the U.S., Sergey Kislyak, on Wednesday would neither confirm nor deny discussing forming a communication back-channel with President Trump's son-in-law Jared Kushner during the transition period.

In an interview with CNN, which took place as he got out of a van in Russia, Kislyak was asked if he had discussed opening secret back channels to the Kremlin with Kushner.

"I've said many times we do not discuss the substance of our discussions with our American interlocutors out of respect to our partners," Kislyak said.

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In May, CBS News confirmed that when Kushner met Kislyak in December, Kushner discussed setting up a "back channel" for communications between the Trump transition team and Russian officials, according to a source familiar with the intelligence gathered at the time. The development was first reported by The Washington Post.

Asked Wednesday whether he's a Russian spy and whether he recruited any members of the Trump administration, Kislyak said, "Nonsense. You should be ashamed because CNN is the company that keeps pointing to this allegation. It's nonsense."

He also offered a fairly bleak prediction of U.S.-Russia relations in the future.

"I'm afraid it's going to be difficult. And it's not because of us. It's because [of] the U.S. political dynamics. The anti-Russian law simply isn't going to help Russian-American discussions."

He added that the new U.S. sanctions against Russia will "spoil [the] ability of both countries to resume normalcy in our relations."

Kislyak was of course seen with Mr. Trump in the Oval Office the day after James Comey was fired as FBI director, in photos released by the Russian Foreign Ministry.

Kislyak, 66, served as Russia's envoy to the U.S. between 2008 and last week and spent his career as a diplomat, spanning both the Cold War and the Russian Federation since the collapse of the Soviet Union.

CBS News' Arden Farhi contributed to this report.