Pentagon spokesman John Kirby said Monday that while there has been combat in the Donbas region in eastern Ukraine for some weeks, it is part of Russia’s ongoing "shaping" operations for a future offensive, and not the offensive itself.

"We're not disputing that there's not combat going on in the Donbas," Kirby said. "What we're saying is that we still consider that what we're seeing to be a piece of shaping operations."

“That the Russians are continuing to set conditions for what they believe will be eventual success on the ground by using, by putting, in more forces, putting in more enablers, putting in more command and control capability for operations yet to come," he said.

Asked to clarify his answer, Kirby replied: "We believe that the Russians are shaping and setting the conditions for future offensive operations. We also see ... that there is active combat going on right now in the Donbas as there has been for the last several weeks."

Kirby described the fighting in the besieged port city of Mariupol as part of that since the Russians are "trying to set the conditions for more aggressive, more overt and larger ground maneuvers in the Donbas."

He added that the Russians have also continued to flow in artillery, helicopters, enabling troops and more command and control units as part of the groundwork for that upcoming operation.

Kirby said that the U.S. believes that Russia has reinforced the number of battalion tactical groups in eastern and southern Ukraine as part of their preparations for a large operation in the Donbas region.

-ABC News' Conor Finnegan, Luis Martinez

The U.S. is still assessing what the Russians were attempting to strike in Lviv in western Ukraine on Monday, according to Pentagon spokesman John Kirby.

Kirby said he would not describe Monday's airstrike as a "bombardment" and said he did not know Russia's intent.

"We don't have a clear sense of battle damage assessment about what they were targeting and what they hit. At this time, we don't have any indication that Western aid was targeted and/or hit or destroyed," Kirby said.

-ABC News' Luis Martinez

The U.S. will offer temporary protected status to Ukrainians already in the country as of April 11, according to a new notice from the Department of Homeland Security in the Federal Register.

The Biden administration announced last month that it would offer Ukrainians this legal basis to stay in the U.S. if they had arrived before March 1. This new notice means that Ukrainians who have been in the U.S. as of April 11 can apply for the legal status, which will remain in effect for 18 months -- until Oct. 19, 2023.

U.S. Citizenship and Immigration Services estimates that about 59,000 Ukrainians could be eligible, according to the Federal Register notice.

Andriy Yermak, head of the Office of the President of Ukraine, has tweeted about the change, which he said was made at the Ukrainian government's request.

-ABC News' Conor Finnegan

There are now 76 Russian battalion tactical groups -- each made up of about 800 to 1,000 troops -- inside Ukraine, all in the south or east of the country, a senior U.S. defense official said Monday. Last week there were 65 battalion tactical groups.

There are about 22 additional battalion tactical groups in the north of Ukraine, most likely refitting and resupplying after being depleted from earlier combat, the official said.

The besieged port city of Mariupol is still under threat of missile and artillery bombardment as Ukrainian forces continue to fight to push back Russian troops, according to the official.

Kyiv and Lviv are under long-range fire, the official said. Russian long-range bombers have hit both cities with air-launched cruise missiles over the last couple of days, the official said.

"Our initial assessment is that they were going after primarily military targets, or what they believed to be military targets," the official said.

The U.S. is sending 18 howitzers -- short cannons used to fire projectiles -- to Ukraine and plans to begin training Ukrainians on the artillery in the coming days, the official said.

-ABC News' Matt Seyler

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan