FBI Director James Comey says he is closely watching the bureau's investigation of Hillary Clinton's emails "to make sure it's being done well."

Comey says he feels "pressure" to do the investigation well and promptly, adding that "between those two things we will always choose well."

Meeting with reporters at FBI headquarters Wednesday, Comey offered few details about the investigation into Clinton's use of a private email server during her time as secretary of state. He refused to say whether the investigation will be completed before this summer's party conventions, saying it was not "tethered to any external deadline."

In response to a question asserting that others holding security clearances would be in jail if they had acted as Clinton had, Comey said there was no "special set of rules for anybody that the FBI investigates."

The issue of Clinton's emails has dogged her throughout her campaign for the Democratic presidential nomination. She has denied any wrongdoing.

Comey previously said that his people investigating the matter "don't give a rip about politics" and that the investigation would be "professional, prompt and independent."

Comey would not say whether the FBI would issue a report on the investigation when it's over.

Comey also spoke about the Islamic State, saying it is his view that it is losing its influence in the U.S. He pointed to a drop in Americans attempting to leave the country to join the group. He said that as recently as early last year up to 10 Americans a month had traveled or attempted to travel abroad to join the group, but since last August, that number had declined to about one a month. Comey said the "Islamic State brand has lost significant power in the U.S."

He said the bureau believes "north of 1,000" people in the U.S. are in danger of becoming radicalized by the group.

Comey said encrypted communications over messaging apps such as WhatsApp, owned by Facebook, have become "essential tradecraft" for terrorist groups like ISIS, although he has no plans to sue the company. The FBI purchased a tool to unlock the iPhone used by one of the San Bernardino, Calif., shooters after Apple refused to write software to bypass the device's encryption. Comey said the FBI remains unable to access information on some 500 other phones, which have different operating systems.

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