Russia's defense ministry claimed Wednesday that a Russian warship and fighter jet fired "warning" shots at the British Royal Navy’s HMS Defender destroyer for encroaching on waters near Crimea in the Black Sea.

The latest: The U.K.'s ministry of defense disputed that any warning shots were fired, saying in a statement, "We believe the Russians were undertaking a gunnery exercise in the Black Sea and provided the maritime community with prior-warning of their activity."

National Security Adviser Jake Sullivan told CNN's "State of the Union" on Sunday that the Biden administration is preparing another round of sanctions against Russia over the poisoning of opposition leader Alexei Navalny.

Why it matters: The news of a potential new sanctions package comes days after President Biden warned Vladimir Putin during their summit in Geneva that if Navalny died in prison the consequences for Russia would be "devastating."

House Intelligence Chairman Adam Schiff (D-Calif.) told CBS' "Face the Nation" Sunday that the United States should "go more on offense" to prevent cyberattacks.

Why it matters: Cyber security is in the spotlight after the recent ransomware attack on America's Colonial Pipeline by Russia-based cybercrime group Darkside.

After eight days of talking on the world stage, President Biden got prickly — then blunt, then reflective — in the final minutes before Air Force One lifted off for home.

Why it matters: One wish that aides to generations of presidents have in common is that when their boss walks away from the podium, he'll keep walking. And reporters know that the most revealing comments often come when an interview or press conference is "over": The newsmaker drops the talking points and is more likely to be real.

President Biden's summit "reset" was less about trying to make a friend out of Russia than reframing what the U.S. believes can be accomplished by engaging with President Vladimir Putin.

Driving the news: The Geneva meeting yielded no immediate breakthroughs beyond agreements about ambassadors returning to work and plans to launch talks on nuclear security. But in classic Biden fashion — aviators on, jacket off and a one-liner about invading Russia he had to clarify was a joke — the U.S. president used a post-summit news conference to explain his approach.

President Biden said he warned Russian President Vladimir Putin during Wednesday's summit that if jailed opposition leader Alexei Navalny dies in prison, the consequences "would be devastating for Russia."

Why it matters: Although the White House had previously warned the Russian government over Navalny's imprisonment, Biden personally delivered the message to Putin on Wednesday.

President Biden said he warned Vladimir Putin in their meeting in Geneva on Wednesday that Russia will face stiff consequences if it conducts cyberattacks on critical U.S. infrastructure or allows opposition leader Alexei Navalny to die.

What he's saying: "Where we have differences, I want President Putin to understand why I say what I say, and why I do what I do. And how we will respond to different actions that harm America's interests," Biden said at a press conference following the summit, which was shorter than expected.

At their summit in Geneva on Wednesday, President Biden gifted Russian Vladimir Putin a crystal sculpture of an American bison — the national mammal of the U.S. — and a pair of custom Aviator sunglasses, according to a White House official.

The big picture: The summit came at a low point in U.S.-Russia relations, as acknowledged by both sides. Biden has said he is not seeking a "reset" in relations, but a more "stable" and "predictable" dynamic between the U.S. and Russia.

Russian President Vladimir Putin said Wednesday that his summit with President Biden was "constructive," and that the countries had agreed their ambassadors would imminently return to their posts in Moscow and Washington.

What he's saying: "Many of our joint positions are divergent but nevertheless I think both sides manifested a determination to try and understand each other and try and converge our positions," Putin told reporters at a press conference following the meetings, according to a translator.

President Biden met with Russian President Vladimir Putin in Geneva for less than four hours of talks on Wednesday, a highly anticipated summit that comes as both sides say U.S.-Russia relations have sunk to a new post-Cold War low.

The latest: At a press conference following the conclusion of the summit, Putin called the talks "very constructive' and announced that the U.S. and Russia's respective ambassadors would return to their posts. Biden called the talks "positive" and stressed in his press conference that his agenda is "for America," not "against Russia."