Donald Trump wants to know: Who does Apple Inc. think it is in refusing to help the Justice Department unlock a phone used by a suspect in the San Bernardino attack just over two months ago?

That was Trump’s comment Wednesday morning in a call to the “Fox & Friends” show after Apple AAPL, -3.08% Chief Executive Tim Cook called a federal judge’s order “an unprecedented step which threatens the security of our customers” in a message posted on Apple’s website. Cook said the company will oppose the order.

“Who do they think they are? No, we have to open it up,” said Trump, the front-runner for the Republican presidential nomination. Listen to Trump:

Cook’s letter was posted early Wednesday. The order calls on Apple to disable certain security measures on the phone, once used by Syed Rizwan Farook, a suspect in the attack in which 14 people were shot and killed in the California city. Farook and his wife Tashfeen Malik died in a shootout with police after the attack.

Messages left with the campaigns for Hillary Clinton, Bernie Sanders, Jeb Bush, Marco Rubio, Ted Cruz, John Kasich and Ben Carson weren't immediately returned.

White House spokesman Josh Earnest told reporters on Wednesday that the Justice Department is asking Apple to unlock one device, not create a new “backdoor” to its products. Meanwhile, Sen. Dianne Feinstein, a California Democrat who is vice chairman of the Senate Select Committee on Intelligence, said in a statement it is not “unreasonable” for Apple to provide technical assistance.

“I understand there are privacy concerns, but in this case the phone is owned by the county — which has consented to a search — and there is a valid search warrant,” Feinstein said.

Sen. Richard Burr, the North Carolina Republican who is chairman of the intelligence committee, said in a statement: “Court orders are not optional and Apply should comply.”

Trump has been outspoken in calling for aggressive action by the U.S. to protect its citizens, including supporting “enhanced interrogation techniques” in a USA Today op-ed on Monday.