The U.S. State Department is raising “concerns” about signs that Ukraine may be backtracking on its commitment to fight corruption, jeopardizing support for Kyiv in the West.

A campaign against public corruption through stepped up enforcement and reforms of the judicial system has been a key requirement for Ukraine to obtain loans and closer relations with the European Union, United States, and International Monetary Fund, as reported by Radio Free Europe/Radio Liberty.

U.S. State Department spokeswoman Heather Nauert said in a statement late on December 4 that “recent events — including the disruption of a high-level corruption investigation, the arrest of officials from the National Anti-Corruption Bureau of Ukraine (NABU), and the seizure of sensitive NABU files – raise concerns about Ukraine’s commitment to fighting corruption.”

Nauert’s statement apparently refers to the disruption last month of an advanced undercover operation investigating corruption in Ukraine’s Migration Service described on the website of NABU, an anticorruption agency set up recently in exchange for the EU’s relaxation of visa restrictions for Ukrainians in the eurozone.

The NABU said its investigation into allegations that the migration service took bribes to provide foreigners with Ukrainian citizenship, passports, and residency permits began in April. NABU said it found one of the migration service’s deputies was a “leader of the criminal organization” taking bribes within the agency, and she offered to arrange to provide Ukrainian passports and residency permits to an embedded special agent for about $30,000 apiece.

But when the undercover agent arrived at a scheduled November 29 meeting to provide the migration official with half the bribe money, he was arrested by officers of the Ukrainian security service, NABU said on its website, thus the operation “was disrupted.”

Nauert said in the U.S. statement: “These actions appear to be part of an effort to undermine independent anticorruption institutions that the United States and others have helped support. They undermine public trust and risk eroding international support for Ukraine.”

Nauert noted that U.S. Secretary of State Rex Tillerson has said: “It serves no purpose for Ukraine to fight for its body in [the] Donbas if it loses its soul to corruption. Anticorruption institutions must be supported, resourced, and defended.”

“Reflecting the choice of the people of Ukraine, the United States calls on all branches of Ukraine’s government to work together cooperatively to eliminate corruption from public life,” Nauert said. “Eliminating corruption is key to achieving stability, security, and prosperity for all Ukrainians,” she said.