Secretary of State John Kerry wouldn't weigh in Friday on the implications of the apparent Chechen ties of the suspects in the Boston bombings as he took questions from reporters.

"At this point law enforcement officers are carrying out an ongoing investigation and, frankly, they're at some critical stages here. And it would just be entirely inappropriate for me to be commenting on the tick-tock around the larger issues outside of it," he said at the State Department.

Pressed again, he declined to comment. "I'm not going to get into speculation, I'm not going to deal with a hypothetical."

The FBI, he said, "is the lead entity with respect to this investigation and they will lay out the details of contacts and information at the appropriate moment."

He added: "The important thing now is, the president has said: we're going to find those responsible and bring them to justice. We're part of the way there, and the president tends to finish that job.