Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

Russia's decision to blockade a steel plant in Mariupol "likely indicates a desire to contain Ukrainian resistance" in the strategic port city "and free up Russian forces to be deployed elsewhere in eastern Ukraine," the U.K. Ministry of Defense said Friday in an intelligence update.

The Azovstal Iron and Steel Works plant is the last holdout for Ukrainian fighters in besieged Mariupol.

"A full ground assault by Russia on the plant would likely incur significant Russian casualties, further decreasing their overall combat effectiveness," the ministry said.

Meanwhile, heavy shelling and fighting continues across eastern Ukraine's Donbas region as Russian forces seek to advance further toward settlements including Krasnyy Lyman, Buhayikva, Barvinkove, Lyman and Popasna, "as part of their plans for the region," according to the ministry.

"Despite Russia's renewed focus they are still suffering from losses sustained earlier in the conflict," the ministry added. "In order to try and reconstitute their depleted forces, they have resorted to transiting inoperable equipment back to Russia for repair."

Russian President Vladimir Putin will have a telephone conversation with European Council President Charles Michel on Friday before meeting with permanent members of the Russian Security Council, according to Kremlin spokesman Dmitry Peskov.

"Putin will now have an international conversation," Peskov told reporters Friday. "It will be the President of the European Council, Michel. And then during the day, Putin is scheduled to have an operational meeting with the permanent members of the Security Council."

Attorney General Merrick Garland announced Thursday during an unrelated news conference that U.S. and international allies have been in contact with Ukraine’s prosecutor general and is "helping in the collection of evidence and the preservation of evidence relating to possible war crimes."

Earlier this month President Joe Biden called Russian's killings of civilians a war crime and said Russian President Vladimir Putin needs to be held accountable.

-ABC News' Beatrice Peterson

Russian President Vladimir Putin's comments Thursday morning claiming victory in Mariupol was "yet more disinformation" from Russia's "well-worn playbook," State Department spokesperson Ned Price told reporters.

Price called Putin's comments an attempt to "distract from what can only be considered the underperformance of Russia's military forces and its failure to achieve its original objectives in Ukraine."

Price said Ukrainian forces in Mariupol "continue to hold their ground."

"Their ferocious stand stands in stark contrast to the plummeting morale that we've seen among Russia's forces. It stands in stark contrast to the tactics that we've seen Russia impose against those in Mariupol," he added.

Price said the U.S. has called for humanitarian access -- aid to get in and people to get out -- and has supported humanitarian groups working to do so. But he blamed Russia's attacks on humanitarian corridors for preventing it from happening.

-ABC News' Conor Finnegan