U.S. Secretary of State Antony Blinken is in Ukraine for meetings Thursday with President Volodymyr Zelenskiy, Prime Minister Denys Shmyhal and Foreign Minister Dmytro Kuleba.
"This will be an important opportunity to discuss continued Russian aggression and to underscore the need for maintaining both the pace of and focus on reforms with our Ukrainian partners," Blinken tweeted after arriving in Kyiv.
Late last month, senior U.S. and European Union officials said roughly 150,000 Russian troops massed along the border of Ukraine and in Crimea.
Blinken is expected to restate that the United States will not recognize Russia's 2014 annexation of the Crimean Peninsula, and to call for its return to Ukraine.
He will also call on Russia to uphold its commitments under the Minsk agreements to end the conflict in eastern Ukraine. Since 2014, Russia has been supporting pro-Russian separatists in the eastern region of Donbas.
The State Department said Blinken will also encourage institutional reforms in Ukraine, which the State Department called "key to securing Ukraine's democratic institutions, economic prosperity, and Euro-Atlantic future."
Blinken will likely underscore the importance of U.S. economic support for Ukraine.
"Since 2014, the United States has provided Ukraine more than $4.6 billion in total assistance, including security and non-security assistance," according to the State Department.