A top foreign policy aide to President Joe Biden is joining Kamala Harris’s office, adding firepower to the vice president’s team as pressing national security issues command increasing attention inside the White House.

Rebecca Lissner will start as Harris’s deputy national security adviser in the coming weeks, according to Politico. Lissner is currently the acting senior director of the National Security Council’s strategic planning directorate and an expert on U.S. policy toward Russia who has closely advised the administration on the long-term implications of Moscow’s invasion of Ukraine. She has also overseen Biden’s still-to-come National Security Strategy, according to the outlet.