WASHINGTON >> The United States and its allies hit back at Russia’s annexation of four Ukrainian regions on Friday, slapping sanctions on more than 1,000 people and companies, including arms supply networks, as President Joe Biden warned Vladimir Putin he can’t “get away with” seizing Ukrainian land.

The Russian annexation, though expected, escalated an already heated conflict that’s become fraught with potential nuclear implications.

Biden said his administration would support any effort by Ukraine to retake the annexed territories by force, setting the stage for further hostilities. And Ukrainian President Volodymyr Zelenskyy announced that his country would make an “accelerated” bid to join the NATO military alliance, a plan not endorsed by the U.S. or other allies that could add fuel to the fire.

“America and its allies are not going to be intimidated by Putin and his reckless words and threats,” Biden told reporters. He added that Putin “can’t seize his neighbor’s territory and get away with it.”

Russian President Vladimir Putin’s announcement that Russia is incorporating four Ukrainian cities and areas was not unexpected following referendums this week that the West had denounced as shams. And the U.S. and Western allies had previewed what their reaction would be. But the developments dramatically increased tensions to a point not seen since the Cuban Missile Crisis 60 years ago during the Cold War.

Biden had spoken out against the annexation plans last week at the U.N. General Assembly, where a vast majority of other members also voiced support for respecting the territorial integrity of all nations. On Friday, he used the moment to reiterate that the U.S. and NATO allies would not allow Russia to attack any of the nearby NATO members without facing a strong military response.

“America is fully prepared, prepared with our NATO allies to defend every single inch of NATO territory. Every single inch,” Biden said. “And so, Mr. Putin, don’t misunderstand what I’m saying. Every inch.”

While the Biden administration has identified the suppliers of Russia’s weapons and battlefield high-tech as a priority, many of Friday’s other sanctions were in line with penalties already enacted on thousands of Russian individuals and companies, and may have comparatively little impact on the war effort. The administration hopes they will serve to further undermine support for Putin’s invasion among Russia’s elite.