Biden called on Congress to send him a bipartisan national security bill amid Russia's ongoing war in Ukraine.

"If the United States walks away, it will put Ukraine at risk. Europe is at risk, the free world will be at risk," he said.

Biden also had a message for Russian President Vladimir Putin: "We will not walk away," he said to applause.

"We will not bow down! I will not bow down! In a literal sense, history is watching," Biden said.

Many Republicans have been increasingly skeptical of foreign aid to Ukraine versus spending on domestic priorities like the southern border. Biden and the GOP have not been able to agree on new immigration changes, despite a Biden-backed deal in the Senate.

Biden took his first jab at Trump of the night as he called on Congress to provide further assistance to Ukraine in its fight against Russian invaders.

"Ukraine aid is being blocked by those who want to walk away from our world leadership," he said. "It wasn't long ago, when a Republican president named Ronald Reagan thundered, 'Mr. Gorbachev, tear down this wall.'"

Biden continued, "Now, my predecessor, a former Republican president, tells Putin, 'Do whatever the hell you want.' That's a quote. The former president actually said that bowing down to a Russian leader. I think it's outrageous, it's dangerous and it's not acceptable."

Biden dubbed the current time an "unprecedent moment" in America, drawing parallels to his speech Thursday with that of former President Franklin Delano Roosevelt in 1941, right before the U.S. entered World War II.

"Tonight, I come to the same chamber to address the nation. Now, it's we who face an unprecedented moment in the history of the union. And yes, my purpose tonight is to wake up the Congress and alert the American people this is no ordinary moment either," Biden said.

The president warned that "freedom and democracy under assault" both "at home and overseas at the very same time," pushing for aid to Ukraine as it works to fight off Russia's invasion -- adding a warning as Congress proves unable to agree on a bill to send aid to Kyiv.

"If anybody in this room thinks Putin will stop at Ukraine, I assure you he will not," Biden said.

While Biden entered the U.S. Capitol House chambers for his State of the Union address, Secretary of Education Miguel Cardona was announced as the "designated survivor."

The designated survivor is a Cabinet member chosen to remain physically away from the president and vice president in case of an emergency or an attack during the State of the Union.

Cardona will go to an undisclosed location for the duration of the address.

As he told ABC News Senior Congressional Correspondent Rachel Scott he would, disgraced former Republican Rep. George Santos arrived to the House chamber on Thursday night about an hour before Biden's speech begins.

He was seen seated on the GOP side near the aisle -- his normal position when he was a voting lawmaker.

As a former member, Santos retains the privilege of accessing the House floor. He would need to be convicted of one of his criminal charges to be banned from the floor. He has pleaded not guilty.

-ABC News' John Parkinson