WASHINGTON (NEXSTAR) — With no end in sight to Russia’s attack on Ukraine, some U.S. lawmakers say the U.S. needs to step in and take more action to stop Russia.

However, it’s a delicate consideration for lawmakers and the Biden administration to decide how involved the U.S. can get in the conflict in Ukraine due to fears of what Russia would do in retaliation.

Ukrainian President Volodymyr Zelenskyy said Ukraine won’t give up its fight against Russia in the besieged eastern city of Mariupol.

“It is very important for us not to allow them, to stand our ground,” Zelenskyy said, despite warnings from Russia to the remaining troops there to surrender or die.

On CBS Face the Nation, U.S. Sen. Chris Coons (D-DE) says the U.S. shouldn’t give up either.

“the American people cannot turn away from this tragedy in Ukraine,” he said.

Coons advocated for more U.S. involvement in Ukraine.

“I think the history of the 21st century turns on how fiercely we defend freedom in Ukraine. And that Putin will only stop when we stop him,” he said.

On Capitol Hill, more than one U.S. senator said perhaps U.S. troop involvement in Ukraine shouldn’t be completely off the table as Russia shows no signs of backing off its attack on Ukraine.

“The president, in terms of his decisions as commander in chief, needs to look clearly at the level of brutality,” Coons said.

Russia has already sent a warning to the U.S. to stop sending weapons to Ukraine.

U.S. involvement in helping Ukraine has been measured in part because Russia possesses nuclear weapons that some experts fear Russian President Vladimir Putin would use.

Meanwhile, Pope Francis addressed those fears of nuclear war in his Easter Sunday remarks.

“Shall we put an end to the human race, or shall mankind renounce war?” Francis asked.

Another reason the U.S. hasn’t sent troops to defend Ukraine is that Ukraine isn’t part of NATO. So far, President Joe Biden has held firm in his decision the U.S. won’t send troops to fight in Ukraine.