The Russian Foreign Ministry said on Monday that U.S. President Joe Biden missed an important diplomatic opportunity by declining Russian President Vladimir Putin’s challenge to a one-on-one televised debate.

“One more opportunity has been passed up to look for a way out of the dead end in Russia-U.S. ties. Responsibility for that rests fully with the United States,” the Foreign Ministry said.

Kremlin spokesman Dmitry Peskov said on Monday that Biden’s refusal to speak with Putin was meant in earnest, so there are currently no plans for a dialogue between the two leaders.

“Yes, it is true, there are no such plans for today. As far as I understand, the U.S. side is not ready,” Peskov said, somewhat sarcastically alluding to the White House statement on Friday that Biden would meet with Putin “when the time is right.”

Putin challenged Biden to a televised debate on March 18, responding to an interview where Biden called him a “killer” and threatened to make him “pay a price” for allegedly interfering in American elections.

“I want to propose to President Biden to continue our discussion, but on the condition that we do it basically live, as it’s called. Without any delays and directly in an open, direct discussion. It seems to me that would be interesting for the people of Russia and for the people of the United States,” Putin said.

“We could do it tomorrow or Monday. We are ready at any time convenient for the American side,” Putin offered.

Russia also recalled its ambassador to the United States, Anatoly Antonov, in response to Biden’s remarks. The Russian Foreign Ministry said last week Biden’s insult to Putin could cause an “irreversible deterioration of relations” between the U.S. and Russia.

“The most important thing for us is to identify ways of rectifying Russia-US relations, which have been going through hard times as Washington has, as a matter of fact, brought them to a blind alley. We are interested in preventing an irreversible deterioration in relations, if the Americans become aware of the risks associated with this,” the Foreign Ministry said after Antonov was recalled for “consultations.”