"Under President Yanukovich, the Ukrainian Prosecutor General's Office turned into a black hole of corruption and anti-democratic forces," Pyatt said.
"The new Prosecutor General's Office should be in the forefront of a new Ukraine. Our Department of Justice and the FBI are ready to cooperate with a new team of the Ukrainian Prosecutor General's Office," Pyatt added.
Additionally, he indicated Washington's intent to cooperate with Ukraine on enhancing the mobility of Ukrainian border guards and maintaining security at the Russian-Ukrainian border.
Pyatt spoke as the White House is mulling supplying lethal weapons to eastern Ukraine, where the latest ceasefire agreement has been in force since February 14.
Kiev's attempt to tackle corruption is nothing new. Former President and Orange Revolutionary Viktor Yushchenko declared a "War on Corruption" after coming to power in late 2004, only to prompt a schism in his own government.
