White House press secretary Jen Psaki said Wednesday that Russian President Vladimir Putin is "improvising" and "adapting" his strategy in Ukraine.

Speaking to reporters at the White House, Psaki said that officials believe Putin was surprised by the amount of intelligence and information that the U.S. had gathered about Russia's threat to Ukraine, and was not prepared for the Biden administration to make so much of that information public. 

Psaki said officials believe Putin also was not expecting the global community to be as unified this week in its response to Russia's advancement on Monday into the eastern part of Ukraine.

"Our assessment is that [Putin] is improvising, adapting and having to respond and adapt his own actions as we are responding to him," Psaki said. 

Psaki warned that while Putin was making changes to his strategy, Russia continued to be in an "attack position" and said Moscow remained "capable of operationalizing at any time."

U.S. State Department spokesman Ned Price said Wednesday that they are poised to escalate if Russia takes further actions against Ukraine.

Price referenced the U.S.' recent sanctions against the Nord Stream 2 gas pipeline, which Russia had invested $11 billion into, saying that it is "now a hunk of steel sitting at the bottom of the sea." The pipeline's certification was halted by Germany, and the U.S. imposed sanctions against its Russian manufacturer yesterday. 

While Price said the U.S. is willing to engage in further discussions with Russia, they first want to see that Russia is "serious about diplomacy first."

"This is the beginning of our response," he added. "If they escalate further, we will escalate further.

Ukraine officially declared a 30-day state of emergency beginning at midnight, following a vote from the country's parliament on Wednesday. 

Officials in Ukraine have urged their citizens to leave Russia immediately and began calling military reservists to prepare for a possible invasion, NBC News has reported.

"We are aware of the risks that exist from the Russian Federation. We clearly understand that our army is ready to fight back," Ukraine's top security official, Oleksiy Danilov, previously told reporters after he asked lawmakers to approve the state of emergency.

Ukrainians lined up outside a military registration and enlistment office in Kyiv on Tuesday, a day before President Volodymyr Zelenskyy called up some of the country’s military reservists ahead of a possible conflict with Russia.

Liudmyla Yankina, 38, shared pictures and video from the district of Solomianskyi and told NBC News she and her friends had enlisted as reservists.

She said she felt motivated to register after Russian President Vladimir Putin delivered a speech on Monday formally recognizing the independence of two regions in eastern Ukraine — the self-proclaimed “Donetsk People’s Republic” and “Luhansk People's Republic.” 

“I am from Luhansk and when the war started in 2014 I was shocked and didn’t know what to do except run away and evacuate with my mother from shelling,” Yankina said.

“This time everything is different for me,” she added. “Enough is enough. I won’t run away this time. I will stay and defend my country.”

Biden has announced sanctions on the entity and corporate officers behind the Nord Stream 2 pipeline. 

"These steps are another piece of our initial tranche of sanctions in response to Russia’s actions in Ukraine," said Biden in a statement on Wednesday. "As I have made clear, we will not hesitate to take further steps if Russia continues to escalate."

On Tuesday, German Chancellor Olaf Scholz said Germany was taking steps to halt progress on the pipeline, which would have delivered gas to Germany directly from Russia, following the latest developments in the Ukraine crisis. The U.S. has warned that the pipeline could make Germany overly reliant on Russia for energy. 

House Speaker Nancy Pelosi, D-Calif., lashed out at Russian President Vladimir Putin on Wednesday, calling his aggression toward Ukraine “very evil” and likening it to Adolf Hitler’s annexation of parts of Czechoslovakia just before World War II.

“This, my friends, is our moment. This is the Sudetenland — that's what people were saying there,” Pelosi said referring to conversations she had at the Munich Security Conference in Germany over the weekend. “You cannot ignore what Putin is doing. Nobody is, of course, ignoring it, but you cannot take it any lighter than what it is: a total assault on democracy."

Pelosi repeatedly called Putin “a tyrant" as she briefed reporters on her recent trip.

“This is the same tyrant who attacked our democracy in 2016,” she said, referring to Russian interference in the 2016 presidential election.

“This is the same tyrant who is opposed to democracy and wants to minimize, trivialize it, to downgrade it in the eyes of the Russian people," she said, calling Putin's recent order of Russian troops into two regions in eastern Ukraine “a very evil move."

Pelosi said the sanctions that President Joe Biden imposed Tuesday on Russia were “appropriate” and part of a “unified effort” with NATO and other U.S. allies. 

Biden is ready to go “all the way” with stronger sanctions if Putin continues his incursion into Ukraine, Pelosi said. “Let me just say that we haven't seen the depth of these sanctions yet,” Pelosi added.

Ukraine's foreign minister called for "swift, concrete and resolute actions" against Russia in a speech Wednesday to the U.N. General Assembly. 

"If Russia does not get a severe, swift and decisive response now, this will mean a total bankruptcy of the international security system and international institutions, which are tasked with maintaining the global security order," Dmytro Kuleba told representatives. 

"We urge member states to use all available means to protect Ukraine and deter Russia — whatever action you can take is appreciated," he added. 

Kuleba said that, during a speech Monday, Russian President Vladimir Putin "overtly denied Ukraine's right to exist." He said that Putin wanted to "prove that the United Nations are weak, indecisive and unable to defend their core principles" and "that rules do not apply to him."

The Russians are "as ready as they can be" to attack Ukraine, a senior U.S. defense official tells NBC News. 

They have about 80 percent "in forward positions ready to go," and range from about 3 miles from the border to about 30 miles (5 kilometers to 50 kilometers), the official said. 

“They are literally ready to go now," the official added. Russia has brought in "nearly 100 percent" of the forces the U.S. anticipates Putin would need for a large-scale invasion, they said.

The official also said Russia has more than 10 landing ships in the Black Sea with troops on board. The belief continues to be that a large-scale invasion is still Putin's goal, the official added.

Years of Western reluctance to help Ukraine modernize its Soviet-era air defenses have left the country dramatically vulnerable to a massive Russian bombing and missile campaign that could devastate Ukrainian forces before they ever see a hostile tank or soldier.

A confluence of concerns — fear of provoking Russia, worries the technology could fall into Russian hands, doubts Ukraine could operate the systems — prevented the U.S. and its allies from granting Ukrainian requests for sophisticated surface-to-air missiles in the years after Russia seized Crimea in 2014, current and former American officials and defense experts told NBC News.

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