"We're as close as we've ever been to getting peace here in Europe, and have it endure," Whitaker told Fox Business.
Whitaker’s remarks come following negotiations between US and Ukrainian officials over the weekend in Geneva, where they discussed the US-proposed plan to resolve the Ukraine conflict.
The original 28-point peace plan was reportedly revised down to 19 points following the Geneva talks.
US media reported earlier in the day that US Army Secretary Daniel Driscoll held talks with Russian officials in Abu Dhabi on Monday and Tuesday to discuss the new plan.
Russian President Vladimir Putin said last week that Trump's new peace plan could form a basis for a final settlement in Ukraine.