U.S. consumers are already feeling the squeeze. In California, prices for some types of gas has hovered around $6 in recent days; on Tuesday the state average was well over $5.

Republicans on Tuesday largely backed Mr. Biden’s decision to cut off Russian oil, giving the president a rare moment of bipartisan support. But even as they did so, many Republicans once again seized on high prices at the pump to criticize him and his party.

“Democrats want to blame surging prices on Russia,” Representative Kevin McCarthy of California, the House Republican leader, said on Tuesday. “But the truth is, their out-of-touch policies are why we are here in the first place.”

In his remarks, Mr. Biden cast the decision as a moral one, aimed at further crippling Mr. Putin’s economy as Russian forces continued their brutal bombardment of civilians in several of Ukraine’s cities and suburbs after two grueling weeks of war in Europe.

“Ukrainian people have inspired the world and I mean that in the literal sense,” Mr. Biden said. “They’ve inspired the world with their bravery, their patriotism, their defiant determination to live free. Putin’s war has caused enormous suffering and needless loss of life of women, children, and everyone in Ukraine.”

He added: “Putin seems determined to continue on his murderous path, no matter the cost.”

Battles continued to rage across Ukraine on Tuesday as humanitarian officials reported that two million refugees have fled the country seeking safety. But casualties increased as evacuations though supposed “green corridors” continued to come under fire.

About 2,000 civilians were able to escape Irpin, a suburb just northwest of Kyiv, Ukraine’s capital, which has spent days without water, power and heat because of the heavy fighting in the area. In the war-battered city of Sumy, east of Kyiv, one humanitarian corridor lasted long enough to allow hundreds of civilians to escape in a convoy of buses led by the Red Cross.