WATCH: White House decries Russia’s ‘fraudulent’ annexation attempt

U.S. national security adviser Jake Sullivan condemned Russia’s “fraudulent attempt to annex sovereign Ukrainian territory,” calling it a “a flagrant violation of international law” and insisting it has no legitimacy.

Watch the briefing in the player above.

“The United States will never recognize these actions. The world will never recognize these actions,” Sullivan said, speaking at the White House briefing, adding, “We will stay the course as the president told you earlier today.”

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.

“To put it simply, the regions of Donetsk, Luhansk, Kherson and Zaporizhzhia remain Ukrainian territory. Ukraine has every right to continue to defend its sovereignty,” Sullivan said, adding that the United States will “support them at every step of the way for as long as it takes.”

This suggests the U.S. will support the Ukrainians with weapons and ammunition to help them with military action to retake the annexed areas. The U.S. has warned Ukraine in the past not to use American weapons against Russian territory.