Sen. Bob CorkerRobert (Bob) Phillips CorkerBannon: McConnell 'picking up his game' because of our 'insurgent movement' State Dept. spokeswoman acknowledges 'morale issue' The Hill's 12:30 Report MORE (R-Tenn.) said Wednesday that it was critical for Ukraine to hold its election as scheduled on May 25.

“It is critical that the scheduled May 25 election occur, that it be fair and free, and I know that is a priority of this government,” Corker said after visiting Ukrainian leaders. “The stakes are very high.”

Ukrainian security forces are trying to crack down on pro-Russian separatists that have gained control of government buildings. It’s unclear if the violence will be resolved in time to prevent it from affecting the outcome of the upcoming election.

Corker, the ranking member on the Senate Foreign Relations Committee, pledged to pressure the Obama administration to implement more sanctions against Russian banking and energy sectors.

“The greatest immediate threat to the people of Ukraine realizing a better future is the external threat of Russia,” Corker said. “I am very concerned that on our current path, Russia wants Ukraine to fail more than the West wants it to succeed, and that is a dynamic we must change.”

Obama said Thursday that he has “teed up” additional sanctions against Russia because of its suspected involvement with violent pro-Russian separatists in eastern Ukraine.

Congress approved a Ukraine aid bill that included sanctions against Russian leaders involved in the annexation of Crimea. But as Russian President Vladimir Putin seems determined to control more of Ukraine, lawmakers have called for more action to deter Russian forces from entering its neighboring countries.

“This situation is not just about Ukraine; it's also about other vulnerable places like Moldova, and ultimately — if not addressed — other countries in Europe and the former Soviet Union,” Corker said. “It is crucial that we act now to prevent Russia's perverse actions from gaining momentum and affecting other countries in the region.”