U.S. Assistant Secretary of State Victoria Nuland says U.S. sanctions imposed on Russia must remain until the Kremlin keeps Crimea.

"And of course, Crimea sanctions must remain in place so long as the Kremlin imposes its will on that piece of Ukrainian land," she said in a statement before the Senate Foreign Relations Committee on Tuesday.

Nuland also believes that the year 2016 may become a turning point for Ukraine.

"With will and effort on all sides, 2016 can be a turning point for Ukraine. If security can improve in coming weeks, if hostages are returned, if the parties can finalize negotiations on election modalities and other political issues, we could see legitimate leaders elected in Donbas by fall, the withdrawal of Russian forces and equipment, and the return of Ukraine's sovereignty over its border before the end of the year," she said.

In her words, the stakes are as high as ever. "With strong, unified leadership in Kyiv, 2016 can and should be a turning-point year for Ukraine's sovereignty and European future. If and as Ukraine's leaders recommit to drive the country forward, the United States must be there to support them, in our own national interest. At the same time, we must be no less rigorous than the Ukrainian people themselves in demanding Kyiv's leaders take their responsibility now to deliver a truly clean, strong, just Ukraine while they still have the chance," she added.