US media say President Joe Biden's administration has approved a plan for US troops in Poland to assist Americans in evacuating Ukraine if Russia invades.

US service members, mainly from the 82nd Airborne Division, are being deployed to Poland as tensions increase over the buildup of Russian troops along the Ukraine border.

The Wall Street Journal and other media on Wednesday said the troops will start setting up temporary facilities near Poland's border with Ukraine in coming days.

The reports say US troops will not enter Ukraine, but will be prepared to assist any Americans who flee to Poland from Ukraine. An estimated 30,000 Americans currently live in Ukraine.

Pentagon Press Secretary John Kirby on Wednesday said the Biden administration has been advising Americans to leave Ukraine.

He said the 82nd Airborne troops being sent to Poland are "multi-mission capable" and "ready to do a number of contingencies."

Kirby said he can't rule out that these soldiers could be used for evacuation assistance, and that they're going to be prepared to do that.

Regarding the buildup of Russian troops, Kirby said additional capabilities have continued to flow to the Ukraine border and to Belarus over the last 24 hours.