Former ExxonMobil CEO Rex Tillerson, U.S. President-elect Donald Trump's nominee for Secretary of State, testifies during his confirmation hearing before Senate Foreign Relations Committee January 11, 2017. (Alex Wong/Getty)

Former ExxonMobil CEO Rex Tillerson underwent his Senate confirmation hearing for secretary of state on Wednesday, and, in line with President-elect Donald Trump, he criticized China for trade practices, intellectual property theft, expansion in the South China Sea, and failure to rein in North Korea’s nuclear and ballistic missile programs. But Tillerson also added that the U.S. "needs to see the positive dimensions in our relationship with China as well."

“The economic well-being of our two nations is deeply intertwined," he said. "China has been a valuable ally in curtailing elements of radical Islam. We should not let disagreements over other issues exclude areas for productive partnership.”

His mention of China curtailing “radical Islam” immediately proved controversial.

Tillerson: "China has been a valuable ally in curtailing elements of radical Islam." Wait, what?

— Josh Rogin (@joshrogin) January 11, 2017

#Tillerson says #China is an ally in combating terrorism? I don't think so. #Xinjiang https://t.co/NmM9KXbxKz

— Sophie Richardson (@SophieHRW) January 11, 2017

In recent years, China has been hit by a number of terror attacks originating from the far west province of Xinjiang — home to the Muslim Uighur ethnic minority. Some of the higher profile incidents have included a 2013 car-ramming attack in Tiananmen Square and a 2014 knife attack at the Kunming railway station that killed 31 bystanders.

But critics have noted that the Chinese government has stretched its definition of “terrorism” to encompass far less clear-cut instances. “China has defined almost any dissent from its policies [in Xinjiang] as examples of international terrorism,” said Richard Bernstein, former TIME Beijing bureau chief, in a 2014 ChinaFile conversation. “It has also consistently tried to win Western acquiescence in its suppression of the Uighurs by claiming that all Uighur protests, whether peaceful or violent, against China’s harsh rule in Xinjiang amount to terrorism.”

Many Uighurs have long resented Chinese rule of Xinjiang, which, in addition to coordinated terror attacks, has led to violent clashes between Uighurs and the majority Han ethnic group in the region — most notably with 2009 riots in the provincial capital of Ürümqi that left nearly 200 dead.

In response to these incidents, authorities in the region have launched sweeping crackdowns that included outright religious repression. Police sweeps and prohibitions have targeted people for observing Ramadan, wearing traditional Muslim garb, and growing beards, among other restrictions. Measures of this sort may have even sparked a series of events in 2014 that led to a violent clash between authorities and Uighurs that left at least 96 dead. Official government accounts labeled the incident a terror attack; Uighur activists called it a government massacre.

“Given the absence of peaceful avenues of protest and the mounting frustrations of many Uighurs, it is certainly possible that some Uighurs have joined extremist Muslim groups, and perhaps have instigated some of the Uighur violence,” Bernstein said.

Even moderate critics of government policy have been caught up in the government’s crackdown. In 2014, Ilham Tohti — a well-known Uighur scholar and vocal critic of government policies in Xinjiang — was accused by government authorities of supporting terrorists and was sentenced to life in prison for “separatism.”

This situation complicates anti-terrorism cooperation between China and the United States. In 2002, one year after the September 11 terrorist attacks, the George W. Bush administration controversially listed the East Turkestan Islamic Movement — an ambiguously demarcated Uighur separatist group — as a terrorist organization. Critics at the time asserted that the move was done in order to bolster Chinese support for the U.S. War on Terror at the expense of legitimizing China’s repression of Uighurs.

Since the emergence of the Islamic State in Iraq and Syria, the United States has sought to increase counter-terrorism cooperation and intelligence sharing with China. But this sort of cooperation remains controversial and its utility questionable.

In the 2014 ChinaFile conversation, Ely Ratner, deputy director of the Asia-Pacific Security Program at the Center for a New American Security, said that some limited counterterror cooperation is possible and desirable. But China has little interest in entangling itself in Middle East conflicts, the U.S. fears aiding Chinese authorities’ domestic repression, and neither side is willing to give up much meaningful intelligence. “The constraints are likely to overwhelm any incentives,” Ratner said.

Read the full ChinaFile conversation here.