United States Defense Secretary Chuck Hagel said on Thursday his country will retain its military ties with Egypt but more violence by the army could jeopardize the relationship.

Hagel said he had called General Abdel Fattah al-Sisi, Egypt’s defense minister and the central figure in the interim government, to express U.S. concern after Wednesday’s brutal crackdown on supporters of ousted president Mohammed Morsi.

“The Department of Defense will continue to maintain a military relationship with Egypt, but I made it clear that the violence and inadequate steps towards reconciliation are putting important elements of our longstanding defense cooperation at risk,” Hagel said, according to the AFP news agency.

Hagel’s warning follows an earlier announcement from President Barack Obama cancelling a joint exercise due to be held next month because of the Egyptian army’s violent crackdown Wednesday that left hundreds of protesters dead.

“Since the recent crisis began, the United States has made it clear that the Egyptian government must refrain from violence, respect freedom of assembly, and move toward an inclusive political transition,” Hagel said.

“Recent developments, including the violence that has resulted in hundreds of deaths across the country, have undermined those principles.”

Due to the U.S. military’s decades-long ties with the Egyptian army, Hagel has become the Obama administration’s main conduit for communicating with Cairo as the crisis has unfolded.

The Pentagon chief has had more than 15 phone conversations with Sisi since July 2, the day before the army’s coup that removed president Morsi from power.

“In my discussion with Minister Al-Sisi, I reiterated that the United States remains ready to work with all parties to help achieve a peaceful, inclusive way forward,” Hagel added, according to AFP.

Pentagon spokesman George Little insisted that calling off the exercise sent “a clear signal to Egyptian authorities that we’re deeply concerned about recent events in the country.”

More than 600 people were killed in the clashes that took place between the Egyptian military and the Muslim Brotherhood Wednesday.

The deaths occurred when security forces stormed Islamist protest camps in Cairo after a stand-off that had lasted several weeks.

A month-long state of emergency has been imposed by the interim government, which took power after the army removed Morsi from power on July 3. A dusk-to-dawn curfew has been placed on Cairo and 10 other provinces.