Gen. Mark Milley, the U.S. military's top general, told reporters Friday that it's likely too early to tell the impact of the Wagner Group mutiny on Russian President Vladimir Putin.

"We want to know the answer to that question," Milley said when asked at the National Press Club if Yevgeny Prigozhin's mutiny had left Putin weakened. "I don't think we have evidence, conclusive evidence, either way, yet too early to tell."

Milley acknowledged that Ukraine's counteroffensive is making steady progress, but moving slowly -- something he said was not surprising given how tough of a fight it is.

"At the end of the day, Ukrainian soldiers are assaulting through minefields and in the trenches, and this is literally a fight for their life. So yes, sure, it goes a little slow, but that is part of the nature of war," Milley said.

He also noted that the U.S. is considering sending cluster munitions to Ukraine, though no decision has been made.

-ABC News' Luis Martinez

Russian Gen. Sergei Surovikin has apparently been detained, according to a U.S. official. Other details about his status are unclear.

The development follows reports from a senior U.S. official on Wednesday that Surovikin had engaged in discussions with Wagner Group leader Yevgeny Prigozhin about his plans to mutiny.

Prigozhin is now exiled in Belarus.

-ABC News' Luis Martinez

Former Vice President Mike Pence made a surprise trip to Ukraine on Thursday, projecting solidarity against Russia in a way, so far, unmatched by his Republican competitors in the 2024 presidential campaign.

"As I made clear to President [Volodymyr] Zelenskyy today, when I return home, whatever the future holds for me and my family, we're gonna stand for freedom," Pence told reporters. "And I'll do my part to make sure that America continues to stand for the courageous fighters here in Ukraine that are fighting to reclaim their freedom."

Pence visited the sites of atrocities in the early phase of the war, in Irpin and Bucha, among other stops, before meeting with Zelenskyy inside the presidential palace in the capital of Kyiv.

Read more about the trip here.

-ABC News' Libby Cathey and Guy Davies

Ukraine recorded the "largest deterioration" of peace worldwide in the latest global peace report from the international think tank Institute for Economics & Peace.

"The war in Ukraine had a significant impact on global peacefulness, with Ukraine and Russia having the largest and fifth largest deteriorations in peacefulness respectively," the report stated.

Since last year's report, Ukraine fell 14 places to 157th among the 163 countries covered by the report. Due to the conflict, 65% of men in Ukraine ages 20-24 have fled the country or died, according to the report.

-ABC News' Emma Ogao

U.S. President Joe Biden will make a "memorable speech" before world leaders in Lithuania's capital on the final day of a high-stakes NATO summit, according to National Security Council Senior Director for Europe Amanda Sloat.

Biden's remarks on Wednesday afternoon will focus on similar themes to what he said during his speech in Poland in late February marking one year since Russia waged war on Ukraine.

"President Biden will talk about the strength of the NATO Alliance and how it remains a force for global security and stability, as it has for more than seven decades. He'll talk about how NATO is more vital to our shared future and that didn't happen by accident," Sloat told reporters during a press briefing in Vilnius on Wednesday morning.

"As the president has talked about before, Vladimir Putin thought he could break our resolve when he invaded Ukraine. But our NATO allies and our partners around the world responded by coming together to support the brave people of Ukraine as they defend their freedom, their independence and their democracy," she added.

Beyond addressing the strength of the NATO alliance and the importance of standing by Ukraine, Biden will also look to pitch cooperation like we've seen for Ukraine to tackle other major challenges facing the world, "including the climate crisis, emerging technologies, upholding the international rules of the road and expanding opportunities so we build an economy where no one gets left behind," according to Sloat.

-ABC News' Molly Nagle