President Joe Biden said Tuesday there could be some U.S. troop movements in the "nearer term" in Eastern Europe -- and that he would consider personally sanctioning Russian President Vladimir Putin if Russia invades Ukraine -- a day after 8,500 American forces were put on "heightened alert" in the region.

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"If he were to move in with all those forces, it would be the largest invasion since World War II. It would change the world," Biden told reporters in Washington.

MORE: Biden meets with Europeans about Ukraine as US puts 8,500 troops on 'heightened alert' to be sent to region

Asked about what would lead him to deploy the troops staging nearby, Biden said that depends on "what Putin does or doesn't do" but he repeated that American forces would not move into Ukraine.

President Joe Biden talks to reporters about Russia and the crisis in Ukraine as he pays a visit to a small clothing and gifts store on Capitol Hill in Washington, Jan. 25, 2022.
© Leah Millis/ReutersPresident Joe Biden talks to reporters about Russia and the crisis in Ukraine as he pays a visit to a small clothing and gifts store on Capitol Hill in Washington, Jan. 25, 2022.

"I may be moving some of those troops in the nearer term, just because it takes time," Biden said, adding it's not to be "provocative" but to reassure NATO allies whom have reasons for concern.

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"We have no intention of putting American forces, NATO forces in Ukraine. But we -- as I said -- they're gonna be serious economic consequences if he [Putin] moves," Biden added.

MORE: US accuses Russia of 'fabricating a pretext' to invade Ukraine

Amid the escalating tensions, Biden had a one hour and 20 minute conference call from the White House on Monday with the leaders of the European Commission, European Council, NATO, France, Germany, Italy, Poland and the United Kingdom, according to the White House, which said they planned to "discuss diplomacy, deterrence and defense efforts" as well as what would constitute potential sanctions against Russia.

The White House said after the call that Biden and European leaders "reiterated their continued concern about the Russian military build-up on Ukraine's borders" and also discussed "preparations to impose massive consequences and severe economic costs on Russia for such actions as well as to reinforce security on NATO's eastern flank."