U.S. officials say Russia’s lethal shelling in the western part of Ukraine on Sunday, close to the border with Poland, is something that they had anticipated.

“This does not come as a surprise to the American intelligence and national security community,” said U.S. National Security Adviser Jake Sullivan during a Sunday morning appearance on CNN. “What it shows is that Vladimir Putin is frustrated by the fact that his forces are not making the kind of progress that he thought that they would make.”

At least 35 people died and 134 were wounded early Sunday when Russia fired cruise missiles at the International Center for Peacekeeping and Security, a military base in western Ukraine.

The facility, not far from Lviv, is where NATO units train with Ukrainian troops.

NATO troops in Poland are a scant 25 kilometers away, prompting concern that even a misstep by Russia’s military could cause the war to further widen.

“If Russia attacks, fires upon, takes a shot at NATO territory, the NATO alliance would respond to that,” warned Sullivan in an interview on the CBS network’s “Face the Nation” program.

Sullivan and officials from the National Security Council and State Department are scheduled to be in Rome on Monday to meet Chinese Communist Party Politburo Member and Director of the Office of the Foreign Affairs Commission Yang Jiechi.

The discussion will be “part of our ongoing efforts to maintain open lines of communication between the United States and the People’s Republic of China [PRC]. The two sides will discuss ongoing efforts to manage the competition between our two countries and discuss the impact of Russia’s war against Ukraine on regional and global security,” according to NSC spokesperson Emily Horne.

Sullivan on Sunday also responded to growing concern Russia will use chemical weapons in Ukraine.

“We can’t predict a time and place,” said Sullivan on CBS, noting an escalation of rhetoric from Moscow falsely accusing the United States and Ukraine of developing chemical or biological weapons to use against Russian troops.

“That’s an indicator that the Russians are getting ready to do it” and blame it on others, according to Sullivan.

On NBC’s “Meet the Press,” Sullivan said, “We’ve consulted with our allies and partners about it, and we are prepared for that eventuality.” He echoed U.S. President Joe Biden’s warning from last week that Russia would face severe consequences if such weapons are deployed.

In recent days, satellite imagery and media reporters have indicated Russian armored units are poised to relaunch a major offensive to attempt to take Kyiv, the capital of Ukraine, after a lull.

An award-winning American filmmaker and journalist is among the latest casualties of the conflict near the capital.

Brent Renaud died in Irpin, a suburb of Kyiv, according to officials.

“It is one more example of the brutality of Vladimir Putin and his forces as they’ve targeted schools and mosques and hospitals and journalists,” said Sullivan on CNN’s “State of the Union” program.

Renaud, who had previously worked for The New York Times, NBC and HBO, “paid with his life for attempting to expose the insidiousness, cruelty and ruthlessness of the aggressor,” said a statement from Anton Gerashchenko, an adviser to Ukraine’s interior minister.

In recent days, the focus of the invasion has shifted to the besieged southeastern Ukrainian port city of Mariupol.

“We have already evacuated almost 125,000 people to the safe territory through humanitarian corridors,” Ukrainian President Volodymyr Zelenskyy said in a video address released Sunday. “We’re doing everything to counter occupiers who are even blocking Orthodox priests accompanying this aid, food, water and medicine. There are 100 tons of the most necessary things that Ukraine sent to its citizens.”

Ukraine’s Foreign Ministry tweeted Saturday that Russian forces had shelled a mosque in Mariupol where 80 people were sheltering, including some from Turkey.

Seven civilians, including a child, were killed Saturday in a designated humanitarian corridor when Russia struck the convoy, forcing the civilians to turn around, Ukraine’s Defense Ministry said.

Ukraine’s Deputy Prime Minister Iryna Vereshchuk said only nine of 14 humanitarian corridors were open Saturday.

About 13,000 people were evacuated along the routes that had been agreed upon as safe passage exits for civilians, according to Vereschuk.

Also Saturday, a Russian missile attack destroyed a Ukrainian air base in the city of Vasylkiv, according to Mayor Natalia Balasynovych who said an oil depot also was destroyed.

Russia’s Interfax News Agency quoted Balasynovych as saying Russian rockets also destroyed an ammunition depot near Vasylkiv.

Jeff Seldin and Cindy Saine contributed to this report. Some information also came from The Associated Press, Agence France-Presse and Reuters.