Sen. Bob CorkerRobert (Bob) Phillips CorkerDems give muted praise to Pompeo-Kim meeting The Hill's 12:30 Report Corker won’t campaign against Democrat running for Tennessee Senate seat MORE (R-Tenn.) demanded that Europe stand up for Ukraine after it elected a new president on Monday.

“The events in Ukraine have been a wake up call and demand change in the West's approach to central and eastern Europe. We must deal with a new reality together with Poland and our NATO partners,” Corker said. “This is a moment in time where Europe will have to decide whether NATO will be a real or hollowed out alliance.”

Corker, who serves as ranking member on the Senate Foreign Relations Committee, said President Obama should use his upcoming trip to Poland as a way to show U.S. leadership in protecting Ukraine from further Russian invasions.

“When the president travels to Poland he should convey a vision and lay out mid- to long-term plans to strengthen NATO and our Trans-Atlantic relationship as a whole,” Corker said.

Russia has already annexed Crimea and has threatened to take over eastern parts of Ukraine as well, but the United States and Europe have warned Russia to back off and have implemented limited sanctions. 

Corker has called for tougher sanctions against Russia’s energy sector, but Obama hasn’t sought those because European allies don’t want their energy prices to spike since they get most of their natural gas from Russia.

On Monday, Ukraine held a presidential election, which Secretary of State John Kerry called “democratic and peaceful.”