US President Joe Biden has issued a fresh warning to Russia that it will have to "pay a heavy price" if its military move across the Ukrainian border which will be considered an "invasion".
The US has warned that Russia, which has amassed tens of thousands of troops near the Ukrainian borders, could launch an invasion at any point.
Biden on Thursday told reporters that he has been absolutely clear with Russian President Vladimir Putin.
“If any assembled Russian units move across the Ukrainian border, that is an invasion and would be met with a severe and coordinated economic response that I've discussed in detail with our allies and laid out very clearly for President Putin,” he said.
"Let there be no doubt at all that if Putin makes this choice, Russia will pay a heavy price," the US president warned, a day after he predicted that Russia "will move in" on Ukraine and warned of a "disaster for Russia".
Biden stressed on being prepared about cyber attacks, "gray-zone" attacks, and actions by Russian soldiers not wearing their own uniforms.
He alleged that Russia has a long history of using measures other than overt military action to carry out aggression.
"Remember when they moved into the Donbas with 'Little Green Men'? They were dealing with those who were Russian sympathisers and said that Russia had nobody in there," he said.
Soldiers in unmarked uniforms, dubbed "little green men" by some, had swept Crimea in 2014 laying the ground for annexation by Russia.
"We have to be ready to respond to these in a united way with a range of tools at our disposal," Biden said.
Russia is reported to have 100,000 troops at the border, but denies planning to invade Ukraine.
Separately, the Treasury Department has announced sanctions on individuals engaged in influencing activities directed by the Russian government.
"This action was part of our ongoing, longstanding efforts to counter Russia's network of influence efforts and to expose its dangerous, threatening, and ongoing campaign to destabilize Ukraine," White House Press Secretary Jen Psaki said.
In response to a question, she said, "These individuals are at the heart of Russia's destabilising campaign in Ukraine and we stand united with the Ukrainian government."
Psaki stressed that the US is not waiting to take action to counter Russia.
"We see what they're doing and we are disrupting it. These actions are separate and distinct from the broad range of high-impact, severe measures we and our allies are prepared to impose in order to inflict significant costs should they invade," Psaki said.
The White House Press Secretary said the Biden administration is making decisions based on decades of experience of the president and that of his foreign policy team and through consultation with its partners.
"President Putin is going to make the choice he's going to make. Either he is going to decide to invade Ukraine and suffer severe economic consequences or he is going to decide to engage in diplomatic discussions.
"The aggressor is Russia and Putin. They are building up military troops and also pushing out misinformation in Ukraine. That's who we need to keep our focus on and make sure we are educating the public about their actions," Psaki added.