U.S. Ambassador to Ukraine Geoffrey Pyatt welcomes a decision on Ukrainian Prosecutor General Viktor Shokin's replacement and says he hopes for a new impetus to the reform of Ukraine's prosecution system.

"I commend the courageous decision that the President Poroshenko took this week to replace the Prosecutor General. This decision sends a very strong message that Ukraine is serious about implementing reform," he said at a conference in Kyiv on Thursday.

Pyatt said that the president and the Verkhovna Rada had to reach agreement on a new prosecutor general, who should enjoy the support of the Rada and the trust and confidence of Ukrainian civil society. Besides, the ambassador noted that a new prosecutor general should be a dedicated individual committed to a reform of the prosecution system in Ukraine.

"In this regard, Ukraine has a successful model to follow in your new Patrol Police. That institution illustrates how it is possible to radically change a fundamental institution of the rule-of-law system in Ukraine," he said.

In the words of the diplomat, prosecution system reform was "critical to the overall health and effectiveness of the rule-of-law system."

As reported, Ukrainian President Petro Poroshenko said in his address to the nation on February 16 that he had advised Shokin to step down.

On the same day, MP from the Petro Poroshenko Bloc faction Mustafa Nayyem wrote on his Facebook that Shokin had submitted a letter of resignation.

However, the next day Chief of the Main Investigation Department's special investigation division under Ukraine's Prosecutor General's Office (PGO) Serhiy Horbatiuk said Shokin was on leave.

Later head of Petro Poroshenko Bloc faction Yuriy Lutsenko said Shokin had handed over his resignation letter. "He wrote the resignation letter. The president has met with him and received the letter. Until the Verkhovna Rada endorsed it, he is, as I understand, on a sick leave or on a short-term holiday, his is on duty," Lutsenko said.

Shokin was appointed Ukraine's Prosecutor General in February 2015. According to Ukraine's Constitution, the president nominates and dismisses the prosecutor general subject to approval by the parliament. At the same time, the parliament can pass a vote of no confidence in the prosecutor general, after which he or she should resign.