▶ Watch Video: Blinken warns of “massive consequences” for Russia if Putin invades Ukraine

Defense Department officials on Saturday presented President Biden with options to send “several thousand” troops to Eastern Europe to bolster NATO allies, a Pentagon official told CBS News. 

The proposed plans come as Russia continues to build up forces near Ukraine’s border, with no sign of de-escalation. Mr. Biden in December ruled out sending U.S. troops to Ukraine if Russia invades, but his administration has been open to reenforcing NATO allies on the eastern flank. 

Those troops could come from U.S. forces already stationed in Europe or from the United States. As of Sunday night, no units had been given orders to move. 

The administration is considering sending the troops prior to a possible Russian invasion, if NATO allies request them. 

The number of troops sent to the eastern flank could increase tenfold if Russia launches a full-scale invasion of Ukraine, according to the official.

Moscow said it would “respond appropriately” if the U.S. deploys more forces, according to the Reuters news service, citing the Interfax news agency, which was quoting Russian lawmaker Andrei Kartapolov. He heads the Russian parliament’s defense

Pentagon officials presented the options while Mr. Biden was at Camp David over the weekend. Biden was joined in person by National Security Advisor Jake Sullivan and counselor Steve Richetti while other officials participated via secure video conferencing. 

The State Department on Sunday night reissued it’s highest travel advisory urging citizens not to travel to Ukraine because of the potential of Russian military action. The department is also ordering families of U.S. diplomats at the Kyiv embassy to depart the country and urging nonemergency personnel to leave, as well. 

State Department officials warned that Russian military action could come at any point and the embassy would not be in a position to evacuate U.S. citizens if Russia invades. The department urging those who can to leave now on private or commercially-available flights. 

To help the Ukrainian defense forces, the U.S. recently authorized $200 million in security assistance that includes both lethal and non lethal aid. The first shipment arrived in Kyiv Saturday with more to come.