U.S. cluster munitions have arrived in Ukraine, according to Joint Staff Director for Operations Lt. Gen. Douglas Sims.

Sims said that in contrast to Russia, Ukraine is aware of the possible danger to civilians, and does not intend to use them near population centers.

"I don't think that Ukrainians have any interest in using the cluster munitions anywhere near the civilian population, unlike the Russians," Sims told reporters.

-ABC News' Matt Seyler

Coming off a "very productive summit" with NATO allies, President Joe Biden offered a forceful dismissal of Vladimir Putin’s efforts to capture Ukraine during a joint press conference in Helsinki with Finnish President Sauli Niinisto.

"There is no possibility of him winning the war in Ukraine. He's already lost that war," Biden said.

Biden has made similar statements before about Putin’s chances of success, though it’s particularly notable coming off of his meeting with Ukrainian President Volodymyr Zelenskyy and his top military officials Wednesday.

Biden wouldn’t give a timeline for how long he thinks the war can continue, but he ruled out a yearslong offense.

"I don't think the war could go on for years for two reasons. No. 1, I do not think that Russia could maintain the war forever -- No. 1 in terms of their resources and capacity. No. 2, I think that there is going to be a circumstance where eventually, President Putin is going to decide it’s not in the interest of Russia economically, politically or otherwise to continue this war," Biden said.

"But I can't predict exactly how that happens," he continued. "My hope is and my expectation is you’ll see that Ukraine makes significant progress on their offensive and that it generates a negotiated settlement somewhere along the line."

-ABC News' Molly Nagle and Cheyenne Haslett

U.S. National Security Council spokesman John Kirby said Thursday that "it remains to be seen" whether Russia has recovered from last month's brief but chaotic mutiny and if it will have any notable effect on the fighting in Ukraine.

"We don't exactly know what transpired every minute of that event and we don't really know what kind of impact it's going to have on the war in Ukraine," Kirby told ABC News' George Stephanopoulos during an interview on "Good Morning America."

"As we speak, there hasn't really been that much of an effect on the fighting in Ukraine," he added. "The Russians are dug in. The Ukrainians are trying to claw back territory. We're still trying to help them win."

Ukrainian forces are in the midst of a counteroffensive, "all the way from the Donbas area down toward Zaporizhia to the south," according to Kirby.

"They're making halting progress, not as fast [or] as far as they'd like to go, but we're going to do everything we can to give them the tools and capabilities to succeed," he said. "It could be weeks, it could be months of hard fighting here as they try to claim back the rest of their country."

Russian Foreign Intelligence Director Sergey Naryshkin claims he had a phone conversation with CIA Director William Burns in late June, according to the Russian state media outlet TASS.

"The bulk of the conversation was focused on discussing Ukraine and events around it. We gave some thought to and deliberated on what should be done about Ukraine," Naryshkin claimed to the outlet.

The CIA declined to comment about the alleged call.

The alleged conversation lasted "about an hour," according to Naryshkin.

The Russian intel chief noted that arranging an in-person meeting between him and the CIA leader remained a possibility.

-ABC News' Anastasia Bagaeva

Beginning in October, the U.S. will provide F-16 training to a small number of Ukrainian pilots and maintenance teams, Pentagon press secretary Brig. Gen. Pat Ryder said Thursday.

Ryder said "several" pilots and "dozens" of aircraft maintenance personnel will begin training at Morris Air National Guard Base in Tucson, Arizona, after they receive English training in September at Lackland AFB in San Antonio, Texas. The number of pilots and personnel will be determined by Ukraine.

"Although some Ukrainian pilots have English language skills we are anticipating that all the pilots coming to the United States will require some level of additional English language instruction, given the complexities and the specialized English that's required to fly these aircraft," said Ryder.

Sabrina Singh, the Pentagon's deputy press secretary, told reporters earlier this week that the U.S. was open to the idea of training on F-16's if European countries reached capacity though she couldn't define what numbers would constitute capacity. Ryder on Thursday also wouldn't provide a number and said the U.S. wasn't going to wait for the Netherlands and Denmark to reach capacity.

"We know that as the Danes and the Dutch prepare to train those pilots that at a certain point in time in the future, capacity will be reached. So preemptively acknowledging that and leaning forward in order to to assist with this effort is the impetus for why we're doing this now," said Ryder.

Ryder wouldn't get into when F-16 deliveries to Ukraine might begin. Denmark's Prime Minister said over the weekend that the first Danish F-16's could arrive by New Year's.

-ABC News' Luis Martinez