Putin warns that anyone who threatens Russia's security will 'regret' it as he amasses 100,000 troops on Ukraine's borders

• Russian President Vladimir Putin in an annual address warned the West of crossing Russia.
• Anyone who threatens the "fundamental interests of our security will regret their deeds," Putin said.
• Putin's comments came as 100,000 Russian troops have amassed along Ukraine's borders.

Russian President Vladimir Putin in an annual address on Wednesday warned any adversaries who cross Russia's "red line" that they will face an "asymmetric, fast, and tough" response.

"The organizers of any provocations threatening the fundamental interests of our security will regret their deeds more than they have regretted anything in a long time," Putin said, per The New York Times. "I hope no one gets the idea to cross the so-called red line with Russia - and we will be the ones to decide where it runs in every concrete case."

When asked whether the US takes Putin's comments "personally" at a press briefing later on Wednesday, White House press secretary Jen Psaki said, "I don't think we take anything President Putin says personally. We have tough skin."

Putin's speech came as Russia has amassed roughly 100,000 troops on Ukraine's borders, raising alarms across the West. Amid fears of a possible Russian invasion, Ukrainian President Volodymyr Zelensky on Tuesday urged Putin to deescalate tensions and proposed meeting in the Donbass region, where there's an ongoing war between Ukrainian forces and Kremlin-backed rebels.

"Mr Putin: I am ready to go even further and invite you to meet anywhere in the Ukrainian Donbass, where there is a war," Zelensky said in a video address, per Reuters.

"Does Ukraine want the war? No. But is Ukraine ready for the war? Yes," Zelensky went on to say.

Ahead of Putin's speech on Wednesday, there were concerns he might use the address to announce an invasion into Ukraine. But he made no major announcements and did not offer clarity on Russia's military buildup on Ukraine's borders, even as he issued warnings to the West.

Putin's speech also came as he faces ongoing criticism over the imprisonment of his most prominent critic, Alexei Navalny.

Navalny's health has been rapidly deteriorating in recent days, and his allies say the anti-corruption campaigner is on the verge of death. The White House, which is engaged in an escalating diplomat tit-for-tat with Moscow, has warned of consequences for Russia if Navalny dies. The Kremlin critic was poisoned with the Soviet-era nerve agent Novichok in August, in an apparent assassination attempt that has been widely blamed on Putin.