More than 20 countries have accepted an invitation to attend a Ukraine-focused defense talk on Tuesday hosted by the U.S., Pentagon press secretary John Kirby said Friday.

More than 40 NATO and non-NATO countries have been invited to the talks, which will be hosted by U.S. Defense Secretary Lloyd Austin at Ramstein Air Base in Germany, Kirby said.

"The goal is to bring together stakeholders from all around the world for a series of meetings on the latest [Ukrainian] defense needs and … ensuring that Ukraine’s enduring security and sovereignty over the long-term is respected and developed,” Kirby said.

-ABC News' Somayeh Malekian

United Nations Secretary-General António Guterres will meet with Russian President Vladimir Putin and Russian Foreign Minister Sergey Lavrov in Moscow on Monday.

Guterres wrote separate letters to Putin and Ukrainian President Volodymyr Zelenskyy on Tuesday asking to meet "to discuss urgent steps to bring about peace in Ukraine," a U.N. spokesperson said earlier this week.

The international swimming federation FINA said it has suspended swimmer Evgeny Rylov, a Russian Olympic gold medalist, for allegedly attending a March concert where Russian President Vladimir Putin justified the invasion of Ukraine. The suspension will last nine months.

FINA also said Russian and Belarusian athletes and officials won't be invited to any FINA events through the end of 2022.

-ABC News' Christine Theodorou

European Council President Charles Michel and Russian President Vladimir Putin had a call Friday. Michel said afterwards on Twitter that he "strongly urged for immediate humanitarian access and safe passage from Mariupol and other besieged cities all the more on the occasion of Orthodox Easter."

Michel also said he "firmly reiterated" the EU's support for Ukraine and "condemnation and sanctions for Russia’s aggression."

According to the Kremlin's readout of the call, Michel asked Putin to have direct contact with Ukraine President Volodymyr Zelenskyy. The Kremlin said Putin "reaffirmed the well-known position on this matter, noting that such a possibility depends, in particular, on concrete results in the ongoing negotiations between Russian and Ukrainian representatives, during which the Ukrainian side is showing inconsistency and is not ready to seek mutually acceptable solutions."

Mariupol has not yet fallen, despite Russia's demands that Ukrainian troops defending the besieged Ukrainian port city surrender, according to Ukrainian Prime Minister Denys Shmyhal.

"There [are] still our military forces, our soldiers, so they will fight until the end," Shmyhal told ABC News' George Stephanopoulos in an exclusive interview Sunday on "This Week."

Mariupol is a strategic city for Moscow because it would allow Russian forces in the south to connect with troops in eastern Ukraine's contested Donbas region. It would also give Moscow a key port.

Although Mariupol remains under the Ukrainian government's control, Shmyhal said the city's residents are suffering.

"They have no water, no food, no heat, no electricity," he said. "They ask all of our partners to support and help stop this humanitarian catastrophe."

-ABC News' Monica Dunn