The U.S. State Department on Friday was strongly critical of United Nations Under-Secretary General for Counterterrorism Vladimir Voronkov for paying a visit to China’s Xinjiang province, where much of the Muslim population has been herded into re-education camps and the rest is under constant state surveillance.

The U.S. worried Voronkov’s visit might grant international legitimacy to Beijing’s claims that oppressing the Uighur Muslims is reasonable and necessary for China’s national security.

State Department spokeswoman Morgan Ortagus said on Friday that Deputy Secretary of State John Sullivan spoke with U.N. Secretary-General Antonio Guterres about the Voronkov visit:

The deputy secretary expressed that such a visit is highly inappropriate in view of the unprecedented repression campaign underway in Xinjiang against Uyghurs, ethnic Kazakhs, Kyrgyz, and other Muslims.

The deputy secretary noted that Beijing continues to paint its repressive campaign against Uyghurs and other Muslims as legitimate counterterrorism efforts when it is not, and stressed that the UN’s topmost counterterrorism official is putting at risk the UN’s reputation and credibility on counterterrorism and human rights by lending credence to these false claims.

Ortagus repeated the U.S. call for “unmonitored and unhindered access to all camps and detainees in Xinjiang by U.N. human rights officials.”

The World Uyghur Congress (WUC) was even more harshly critical of the U.N., denouncing Voronkov’s trip to Xinjiang as “truly shameful” and an “irrevocable mistake.”

“This official visit, approved by the U.N. General Secretary Antonio Guterres, allows China to link its crimes against humanity in East Turkestan as a necessary counterterrorism measure,” charged WUC President Dolkun Isa.

The U.N. confirmed on Monday that Voronkov visited Xinjiang from June 13-15 at China’s invitation and was “briefed on the implementation of the United Nations Global Counter-Terrorism Strategy and its four pillars.”

The U.N. dismissed criticism from the United States and World Uyghur Congress, insisting Voronkov went to China for routine security consultations because it was the only permanent Security Council member he had not visited since becoming the top U.N. counterterrorism officer.

Voronkov’s statement about his trip did not mention the Uighurs or the re-education camps at all, nor did he reference the demand by U.N. High Commissioner for Human Rights Michelle Bachelet for unrestricted access to Xinjiang.

Sophie Richardson, director of Human Rights Watch, blasted Voronkov for that omission and for failing to “challenge China’s narrative that the problems in Xinjiang are ones of terrorism, rather than human rights abuses.”

Chinese Foreign Ministry spokesman Lu Kang on Monday called American criticism of Voronkov’s visit “ridiculous.”

“The visit was very successful and strengthened cooperation between China and the UN in the field of counter-terrorism. The U.N. also made positive comments on the visit,” said Lu.

“U.S. officials don’t want to hear and see the international community’s fair and objective voice on the situation in China’s Xinjiang. This is nothing new,” said Lu, claiming China has allowed reasonable international access to what Beijing describes as “vocational training centers” in the province. In truth, China has only allowed small and carefully monitored groups, mostly from countries hostile to the West, to take supervised tours of Xinjiang.

“By smearing the Chinese government’s policies and measures in Xinjiang, the United States has interfered in China’s internal affairs, to which China has made clear its solemn attitude and firm opposition on several occasions. This time, the U.S. side made another outrageous remark about Voronkov’s visit to Xinjiang, making groundless accusations against China and the U.N., which is futile,” Lu said.

A U.N. Security Council diplomat told Reuters last week there is some concern within the United Nations about Voronkov visiting Xinjiang, especially if he fails to speak out against the treatment of the Uighurs and other oppressed minorities.

“The visit by Voronkov validates their narrative that this is a counterterrorism issue when we would see it more as a human rights issue,” the diplomat said. “Silence could be seen as implicit acceptance, at worst U.N. complicity.”