Joe Biden and Vladimir Putin are set to speak Tuesday about a build-up of Russian troops near Ukraine, the Associated Press reports. U.S. intelligence officials say the Russian president has gathered roughly 70,000 troops on the border, which they believe signals a potential invasion. Kremlin spokesman Dmitry Peskov has confirmed the plans. The White House did not immediately offer comment, but the AP reports that Biden said Friday he’s “putting together what I believe to be, will be, the most comprehensive and meaningful set of initiatives to make it very, very difficult for Mr. Putin to go ahead and do what people are worried he may do.”

Russia annexed Crimea, under Ukrainian control since 1954, in 2014. The Kremlin has continued to back separatists in the region, and White House press secretary Jen Psaki told the AP on Friday that the conflict so far has cost 14,000 lives.