The Biden administration is weighing sending military advisers and new equipment including weaponry to Ukraine as Russia builds up forces near the border and US officials prepare allies for the possibility of another Russian invasion, multiple sources familiar with the deliberations tell CNN.

The discussions about the proposed lethal aid package are happening as Ukraine has begun to warn publicly that an invasion could happen as soon as January. The package could include new Javelin anti-tank and anti-armor missiles as well as mortars, the sources said, writes CNN.

Air defense systems, such as stinger missiles, are also under consideration, and the Defense Department has been pressing for some equipment that would have gone to Afghanistan - like Mi-17 helicopters - to instead be sent to Ukraine. The Mi-17 is a Russian helicopter that the US originally purchased to give to the Afghans. The Pentagon is now weighing what to do with them after the US withdrawal from Afghanistan in August.

But others in the administration are concerned that sending stingers and helicopters could be seen by Russia as a major escalation. And while they are prepared to send some military advisers into the region, it is unclear whether any would go into Ukraine itself, the people said.

Retired Lt. Col. Cedric Leighton told CNN that Javelin antitank missiles “are quite effective against the T-80 tanks which the Russians are actually employing in these efforts against Ukraine right now”. But he noted that any additional assistance to Ukraine undoubtedly risks “further heightening tensions” with Moscow.