Marine Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, on Thursday said Turkey’s potential purchase of a Russian missile defense system will make F-35 deliveries to the NATO ally a “tough issue,” while the U.S. top general also detailed plans to meet with Google [GOOG] next week over concerns with the company’s involvement in China.

Dunford, speaking at an Atlantic Council event, highlighted concerns over Russia and China’s increasing role as a competitor with the United States amid their push to operate at levels below armed conflict.

Marine Corps Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff

Regarding Turkey, Dunford said the White House and Congress will have to make tough decisions if Ankara follows through on its purchase of the Russian-built S-400 missile defense system.

“This issue, the S-400, is a tough issue,” Dunford said. “I would just say this, because I merely provide advice I don’t make decisions, but I think both the executive branch of our government and legislative branch of our government are going to have a hard time reconciling the presence of the S-400 and the most advanced fighter aircraft that we have, the F-35.”

Lawmakers have previously raised the possibility of removing Turkey from the F-35 program if it follows through with the S-400 purchase, which Pentagon officials previously said could allow  Russia to gain access to sensitive military information if the systems were integrated together.

“Our position has been made very clear to Turkey, and we’re hopeful that we can find a way through this. But it’s a tough issue,” Dunford said.

Dunford also said he plans to meet with Google officials next week over concerns the company’s work in China could inadvertently assist the country’s military.

“If a company does business in China, they are automatically going to be required to have a cell of the communist party in that company. That is going to lead to that intellectual property from that company finding its way to the Chinese military,” Dunford said.

During a Senate Armed Services Committee hearing last week, Dunford made the same point that Google’s work in China could be benefiting its military amid continued attempts to go after sensitive U.S. military intellectual property.