President Joe Biden pledged on Thursday the United States will never recognize Russia's claims on Ukraine's sovereign territory as the United States prepared new sanctions to impose once Moscow annexes new areas of Ukraine.

Speaking to Pacific island leaders, Biden denounced referendums that pro-Russian forces conducted in areas of Ukraine as an "absolute sham," saying the results were "manufactured in Moscow."

The United States is working with allies on sanctions to impose once Russia annexes new areas of Ukraine. Russian President Vladimir Putin will begin annexing four Ukrainian regions to Russia on Friday, and the U.S. response is expected to follow quickly.

“The United States, I want to be very clear about this, United States will never, never, never recognize Russia's claims on Ukraine sovereign territory," Biden said.

The sanctions are expected to target "individuals and entities inside and outside Russia that provide support to this action," the White House said on Wednesday.

“Russia's assault on Ukraine in pursuit of imperial ambitions is a flagrant, flagrant violation of the UN Charter, and the basic principles of sovereignty and territorial integrity," said Biden. (Reporting by Jarrett Renshaw, Steve Holland and Nandita Bose; Editing by Leslie Adler and Toby Chopra)