There is his address to the Ukraine Rada, in which he says, "It’s not enough to set up a new anti-corruption bureau and establish a special prosecutor fighting corruption. The Office of the General Prosecutor desperately needs reform."

Biden-Poroshenko, February 11, 2016: The leaders also discussed the political situation in Ukraine, agreeing that it is essential for Ukraine to continue to take action to root out corruption and implement reforms.

Biden-Poroshenko, February 18, 2016: The Vice President also commended President Poroshenko’s decision to replace Prosecutor General Shokin, which paves the way for needed reform of the prosecutorial service.

There wasn't any secret that the U.S. was pushing Ukraine for reform. The International Monetary Fund threatened to halt a bailout program for Ukraine unless the country addressed its corruption issues.