The U.S. is not only sanctioning Russia, but sanctioning 24 Belarusian officials, business people, defense agencies and firms, state-owned companies, and banks and financial institutions for "Belarus's support for, and facilitation of" Russia's invasion of Ukraine, the Treasury Department said in a statement.

"The Lukashenka regime has continued to erode democracy in Belarus and has become increasingly subservient to Russia in the process," the Treasury Department claimed.

The targets include two state-owned banks which the department says are "among the most important banks in Belarus." Along with sanctioning Russia's banks, which are very involved in Belarus's economy, "a significant portion of the Belarusian financial sector is now subject to U.S. sanctions," the department said.

The other major target is Belarus' defense industry, with defense firms, defense business leaders, the defense secretary and the State Secretary of the Security Council of Belarus all hit.

-ABC News' Conor Finnegan

The Federal Aviation Administration said it's now prohibiting U.S. airlines from operating over Ukraine, Belarus and parts of western Russia. 

Previously the FAA was only prohibiting U.S. airlines from operating over eastern Ukraine.

This ban does not apply to the military.

-ABC News' Mina Kaji, Amanda Maile

President Joe Biden on Thursday authorized "additional strong sanctions" against Russia.

"This is going to impose severe cost on the Russian economy both immediately and overtime," Biden said in an address. "We have purposefully designed these sanctions to maximize the long-term impact on Russia and to minimize the impact on the United States and our allies."

Biden said he and the other G-7 leaders are in agreement and vowed to "limit Russia's ability to do business in dollars, euros, pounds and yen to be part of the global economy."

Biden said the administration was imposing sanctions on four more major banks, meaning "every asset they have in America will be frozen," he said.

"This includes VTB, the second largest bank in Russia, which has $250 billion in assets," he said.

Biden said they're adding names to the list of Russian elites and family members the U.S. is sanctioning, as well.

"Between our actions and those of our allies and partners, we estimate that we'll cut off more than half of Russia's high-tech imports," Biden said. "We'll strike a blow to their ability to continue to modernize their military. It will degrade their aerospace industry, including their space program. It will hurt their ability to build ships, reducing their ability to compete economically. And it will be a major hit to Putin's long-term strategic ambitions."

However, Biden stopped short of personally sanctioning Russian President Vladimir Putin himself, or cutting Russia off from the SWIFT international banking system.

Biden told reporters that sanctioning Putin is "on the table."

Biden said Putin's attack on Ukraine was premeditated and had been planned for months.

"For weeks we have been warning that this would happen, and now, it's unfolding largely as we predicted," he said.

"Putin is the aggressor. Putin chose this war. And now he and his country will bear the consequences," Biden said.

The U.S. Treasury Department in a statement said it's "taking action against Russia’s top financial institutions, including sanctioning by far Russia’s two largest banks and almost 90 financial institution subsidiaries around the world."

The department said it's also "sanctioning additional Russian elites and their family members and imposing additional new prohibitions related to new debt and equity of major Russian state-owned enterprises and large privately owned financial institutions."

"This will fundamentally imperil Russia’s ability to raise capital key to its acts of aggression," the department said. "These actions are specifically designed to impose immediate costs and disrupt and degrade future economic activity, isolate Russia from international finance and commerce, and degrade the Kremlin’s future ability to project power."

Secretary of Defense Lloyd Austin, at the direction of the president, has ordered 7,000 more U.S. troops to Germany "to reassure NATO Allies, deter Russian aggression and be prepared to support a range of requirements," a senior defense official said.

The troops are expected to deploy in the coming days, the official said.

-ABC News' Matt Seyler

While the Russian Ministry of Defense said some of its troops positioned near Ukraine's border would begin returning to their bases, Secretary of State Antony Blinken told ABC's "Good Morning America" on Wednesday that the U.S. has seen "no meaningful pullback" and described the situation as "deeply, deeply concerning."

"On the contrary, we continue to see forces, especially forces in the vanguard of any renewed aggression against Ukraine, continuing to be at the border, to mass at the border," Blinken said, emphasizing the choice to deescalate is squarely on Russian President Vladimir Putin.

"President Putin's put in place the capacity to act on very short notice," he said. "He can pull the trigger -- he could pull it today. He could pull it tomorrow. He could pull it next week. The forces are there if he wants to renew aggression against Ukraine."

Amid some tensions between U.S. and Ukrainian officials over the level of urgency here, Blinken defended Ukrainian President Volodymyr Zelenskyy, saying the former comedian is "taking it very seriously. He's trying to maintain calm. He doesn't want his people to panic. That's the right thing to do. But I think the Ukrainians are taking it very, very seriously."

ABC News Anchor George Stephanopoulos asked Blinken directly if the threat of attack in Ukraine is "today greater than it was yesterday."

"From day to day, George, you can't say it's higher or lower. It's there. It's there. It's real. We haven't seen a pullback. We'd like to see one. If we see one, we would welcome it," Blinken said. "We're prepared for diplomacy. We're prepared for aggression prepared either way."