Pentagon officials said Friday that Russia has staged enough troops near the Ukrainian border to cause significant casualties if it chooses to invade.
Secretary of Defense Lloyd Austin told reporters Friday that he doesn't believe Russian President Vladimir Putin has made up his mind on whether to invade Ukraine, but he has moved enough troops into the region to give him a range of options.
If war were to break out on a scale and scope that is possible, the civilian population will suffer immensely, according to Gen. Mark Milley, chairman of the Joint Chiefs of Staff.
More than 100,000 Russian troops are now near Ukraine, including ground personnel, air and naval forces, logistical resources and others, according to Milley.
Defense officials told the Wall Street Journal that Russia has moved medical units and blood supplies to the Ukrainian border in preparation for a full invasion.
The Russian government has denied that it wants to invade Ukraine, and when it first began building up troops near the Ukrainian border last year, Putin's spokesman framed the actions as internal troop movements of little consequence to other countries.
It is easier to move equipment over frozen soil in the winter than it is in the summer. The White House told reporters that Biden told Zelenskyy that Russia could invade next month.
Since Russia invaded and annexed Ukraine's Crimean peninsula in the summer of 2014, there has been more tension between the two countries. Russia is trying to prevent Ukraine from drifting toward the West because it shares a long border with the country. After ousting a pro-Russia president in 2014, Ukraine expressed an interest in joining the NATO organization for more than a decade.
In recent weeks, Russian, U.S. and European officials have looked for a diplomatic solution to the recent troop build up near Ukraine, but it is not clear whether this frenzied effort will succeed. Putin wants NATO to reduce its military presence in other Eastern European member states that were once part of Moscow. Putin accused Western countries of ignoring his security concerns after the United States and NATO cast these demands as non-starters.
The Biden Administration has threatened a range of broad economic sanctions if Russia invades, though experts say Russia has worked in recent years to cushion the blow of possible Western penalties by shoring up its foreign currency reserves. It could be difficult to coordinate any financial sanctions with European countries that import large amounts of natural gas from Russia. The Pentagon put up to 8,500 U.S. troops on alert this week for possible deployment to Eastern Europe, though Biden said Tuesday he doesn't intend to send combat troops.
Western diplomats are urged to avoid stirring panic by the Ukrainian officials. Zelenskyy said at a Friday press conference that there are no tanks in the streets and that tensions aren't necessarily higher than they were last spring.
What to know about the Russia talks so far, and what to watch for next.
The White House disputes the account of the Biden call with the Ukrainian President.