According to US media reports, around 2,000 troops will be sent from Fort Bragg, North Carolina to Poland and Germany, while another 1,000 already in Germany will be moved to Romania.

"The Department of Defense will reposition certain Europe-based units further east, forward-deploy additional US-based units to Europe, and maintain the heightened state of readiness of response forces" to meet commitments to NATO, the administration official said.

"These forces are not going to fight in Ukraine. They are not permanent moves. They respond to current conditions," the official said, referring to Russia's placement of more than 100,000 troops along with heavy offensive weapons along Ukraine's border.