MOSCOW, RUSSIA - FEBRUARY 23:  Russian President Vladimir Putin attends a wreath laying ceremony at the tomb of the unknown soldier to mark the Defender of the Fatheland Day on February 23, 2015 in central Moscow, Russia. Originally known as 'Red Army Day' and later observed as 'Soviet Army and Navy Day', it was decreed a state holiday in 2002 after being renamed 'Defender of the Motherland Day'. The holiday marks the foundation of Red Army in 1918 and focuses on achievements of military forces and veteransRussian President Vladimir Putin marks the Defender of the Fatheland Day in 2015 in central Moscow, Russia, with military officials surrounding him.

The Biden administration warned Monday that Russian forces are expected to intensify their military operations in Ukraine.

Jake Sullivan, a national security advisor, told reporters at the White House that when Russia started this war, it wanted to take control of the capital of Kyiv and replace the Zelensky government.

Sullivan said U.S. officials believed the Kremlin was changing its goal in the war.

Russian forces on the ground in Ukraine have been beset with a number of logistical problems over the past five weeks.

Sullivan said that Russia will surround and overwhelm Ukrainian forces in eastern Ukraine.

Air and missile strikes across the rest of the country will likely cause military and economic damage, and cause terror, as a result of Russia's renewed ground offensive in eastern Ukraine.

FILE PHOTO: An aerial view shows a residential building destroyed by shelling, as Russia’s invasion of Ukraine continues, in the settlement of Borodyanka in the Kyiv region, Ukraine March 3, 2022. Picture taken with a drone. 

A Pentagon official who spoke on the condition of anonymity said that the Kremlin has moved most of its forces to Belarus.

The Pentagon believes that the Russian troops are being resupplied with more manpower in Belarus before they head back to the fight in Ukraine, according to an official. The Pentagon believes most of the troops will move to the Donbas region, according to an official.

The official said that the US believes the majority of Russian forces are still in Ukraine.

John Kirby didn't give any details about how the U.S. expects Russian forces to reorganize.

We don't believe that this is a complete withdrawal from the war effort. Kirby said that the main point was that these guys are not going home.

Sullivan didn't give a time frame for how long the U.S. expects the war to last.

Sullivan said that the next phase could be measured in months or longer.