US President Joe Biden on Monday held a video call with European allies as Western nations warned the threat of a Russian invasion of Ukraine remained high and the United States put thousands of troops on alert to be sent to the region if needed, ABC News reports.

The call was 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. It lasted 1 hour and 20 minutes, the White House said.

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."

"The leaders underscored their shared desire for a diplomatic resolution to the current tensions and reviewed recent engagements with Russia in multiple formats," the statement from the White House added.

The conversation came a day after the State Department ordered the families of all American personnel at the US Embassy in Ukraine to leave the country amid heightened fears of a Russian invasion.

The department told the dependents of staffers at the US Embassy in Kiev that they must leave the country. It also said that non-essential embassy staff could leave Ukraine at government expense.

Hours later, the State Department warned American citizens not to travel to Russia amid tensions with Ukraine.

“Do not travel to Russia due to ongoing tension along the border with Ukraine, the potential for harassment against US citizens, the embassy’s limited ability to assist US citizens in Russia, COVID-19 and related entry restrictions, terrorism, harassment by Russian government security officials, and the arbitrary enforcement of local law,” the warning read.

Before Monday’s conversation, the Pentagon announced that Defense Secretary Lloyd Austin had placed around 8,500 US-based troops on "heightened alert" for rapid deployment to assist NATO if needed.

No decision to deploy them had been made, though, according to Pentagon spokesman John Kirby, who noted that the US could also offer troops already stationed in Europe.