Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

Russian Deputy Foreign Minister Sergey Ryabkov on Tuesday denied allegations that Russia might be planning to use biological or chemical weapons in Ukraine.

"We have neither of these," Ryabkov told reporters in Moscow. "What the Americans are saying are malicious insinuations -- we've heard them all the time and we've given exhaustive answers to them for a long time. The problem is, the U.S. has no habit of listening to anyone but itself."

Ryabkov's comments came after U.S. President Joe Biden accused Russian President Vladimir Putin of falsely claiming that the United States and Ukraine are developing biological or chemical weapons for use against Russia -- rhetoric that Biden said shows Putin is considering using those types of deadly weapons in Ukraine.

"He's already used chemical weapons in the past, and we should be careful of what's about to come," Biden said Monday during remarks at the Business Roundtable's CEO Quarterly Meeting in Washington, D.C.

Russian Deputy Foreign Minister Sergey Ryabkov warned Tuesday that the United States should stop supplying Ukraine with weapons and making threats to Moscow in order to "preserve relations" with Russia.

"They simply need to stop in their escalation, both verbal escalation and in terms of stuffing the Kyiv region with weapons. They need to stop producing threats to Russia," Ryabkov said while answering questions from reporters in Moscow. "Meanwhile, if they do manage to somehow positively influence Kyiv, something that I not just doubt, but I am confident that it will not happen, unfortunately, then I think there will be a certain prospect for normalizing relations."

"For now, we see a downward tendency in relations with our country through the fault of the U.S.," he added. "We regret it, but it does not impact our determination to move toward accomplishing the goals of the special military operation and to adapt to the circumstances related to the American sanctions and the sanctions imposed by European satellites of the U.S. at its behest."

When asked whether Moscow plans to recall its ambassador, Ryabkov told reporters that the future of Russia-U.S. relations depends on Washington.

"A note of protest was passed to the American ambassador yesterday. It said that the current developments put these relations on the brink of a breakup," he said. "There is nothing here beyond what was said there: that the question is about a policy that the U.S. will choose."

U.S. President Joe Biden said Russia has used a hypersonic missile in Ukraine, explaining Monday night that it's "the only thing that they can get through with absolute certainty."

"It's a consequential weapon," Biden said during remarks at the Business Roundtable's CEO Quarterly Meeting in Washington, D.C. "It doesn't make that much difference except it's almost impossible to stop it. There's a reason they're using it."

Biden warned that "the more [Putin's] back is against the wall, the greater the severity of the tactics he may employ," and started to describe false flag operations by Russia, specifically its false claims that the United States and Ukraine are developing chemical or biological weapons for use against Russia.

He said those claims are a "clear sign" he's considering using those types of deadly weapons.

"He's already used chemical weapons in the past, and we should be careful of what - what's about to come," Biden said. "He knows there'll be severe consequences because of the United NATO front, but the point is, it's real."

-ABC News' Justin Gomez

Ukrainian President Volodymyr Zelenskyy acknowledged the Ukrainians defending their country in his address Monday, in which he described the Russian forces as "slaves" whose consciousness has been replaced by propaganda.

Zelenskyy called out to Ukrainians in several cities, including those trapped in the besieged city of Mariupol, telling them, "Never think even for a moment that Ukraine does not remember you."

The Ukrainian president also acknowledged the "heroes emerging among the millions" as Ukrainians continue to take up arms against the invaders.

"Once, ordinary Ukrainians, and now, fighters," Zelenskyy said. "Men and women who stand up for our state. Everywhere — in the south, in the east, in the north, in the center, in the west and abroad."

Zelenskyy urged the public to continue to stand up so the "enemy does not believe that this is a reality."

"We will make them remember that they are not welcome," he said.

-ABC News' Christine Theodorou