Secretary of State Rex Tillerson has appointed an envoy to lead U.S. efforts to resolve the crisis in Ukraine, he announced Friday.

Tillerson tapped Kurt Volker, who previously represented the United States at NATO, to take point on American efforts to end the fighting in Ukraine. The crisis has persisted since 2014, when Russia annexed Crimea and sent special forces into eastern Ukraine in support of a separatist movement, despite Western sanctions on Russia and a pair of ceasefire deals known as the Minsk agreements. The announcement comes the same day President Trump and Russian President Vladimir Putin meet in Germany at the G-20 summit.

"Kurt's wealth of experience makes him uniquely qualified to move this conflict in the direction of peace," Tillerson said in a statement. "The United States remains fully committed to the objectives of the Minsk agreements, and I have complete confidence in Kurt to continue our efforts to achieve peace in Ukraine."

Volker, who served under former Presidents George W. Bush and Barack Obama, declined to sign an open letter from GOP foreign policy experts denouncing Trump during the 2016 election. "[Trump] would actually use it as a bragging right," Volker told Reuters in March of 2016.

Tillerson hinted at his intention to launch a new negotiation effort during a round of testimony on the State Department budget in June. "I think it is important that we be given sufficient flexibility to achieve the Minsk objectives," Tillerson told the House Foreign Affairs Committee. "It is very possible that the government of Ukraine and government of Russia could come to a satisfactory resolution through some structure other than Minsk, but would achieve the objectives of Minsk, which we're committed to. So my caution is, I wouldn't want to have ourselves handcuffed to Minsk if it turns out the parties decide to settle this through a different agreement."

That statement left some lawmakers, and Russian observers, with the impression that Tillerson might be willing to provide Russia with sanctions relief without requiring it to surrender land taken from Ukraine.

"The only thing that Russia understands is tough talk and if they think that we're somehow willing to relax the sanctions on them before they've complied with the Minsk framework and left Crimea, I think it just will encourage Putin to continue his bullying," New York Rep. Eliot Engel, the panel's top Democrat, told Tillerson. "And who knows where he will strike next."

Tillerson tried to reassure Engel. "That is not our intent, nor will we do that," he said. "I'm back to the objectives of Minsk."

But Tillerson also cautioned against lawmakers mandating the imposition of new sanctions on Russia, as 97 senators voted to do.

"I would urge Congress to ensure any legislation allows the president to have the flexibility to adjust sanctions to meet the needs of what is always an evolving diplomatic situation," Tillerson said at the June hearing. "Essentially, we would ask for the flexibility to turn the heat up when we need to, but also to ensure that we have the ability to maintain a constructive dialogue."

Engel signaled an opposition to such flexibility on Thursday, as he faulted Trump for saying that "nobody really knows" who carried out the cyber attacks against the Democratic party during the 2016 elections.

"The president's insistence on denying the truth about Vladimir Putin's aggression leaves me worried about their upcoming meeting," Engel said Thursday. "The White House has inexplicably said the president has no agenda for this meeting, but regardless of what comes from it, Congress must be ready to act upon our return to do what the administration won't and push back against Russia's hostility."