'This Week' Transcript: President Obama

— -- Below is the rush transcript of "This Week" on June 29, 2014. It may contain errors.

ANNOUNCER: Starting right now on ABC's "This Week" -

Security alert: U.S. authorities on edge.

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UNIDENTIFIED MALE: I have never seen a threat matrix so serious.

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ANNOUNCER: New airport worries this holiday week. Pierre Thomas with breaking details.

And President Obama on the growing fears in our exclusive interview.

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STEPHANOPOULOS: Are we under serious threat right now?

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ANNOUNCER: Then breaking overnight. Emergency move from the White House responding to a humanitarian crisis on the border. We're on the ground with the latest.

Hillary under fire. Why is she charging nearly a quarter of a million dollars to speak at a university?

And breaking the silence: the father of the Santa Barbara shooter speaks out. What warning signs were missed?

From ABC News, "This Week with George Stephanopoulos" begins now.

STEPHANOPOULOS: Good morning. We're tracking two developing stories, including a major new response from the White House to that humanitarian crisis on our southern border.

And a new terror threat from the al Qaeda group gaining more control of Syria and Iraq. Their advances raising security fears here at home. ABC senior justice correspondent Pierre Thomas starts us off with the latest.

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PIERRE THOMAS, ABC SENIOR JUSTICE CORRESPONDENT: Right now, sources tell us, at this moment in Syria, al Qaeda bombmakers are trying to design a new generation of explosives, including nonmetallic bombs. And the U.S. government is wrestling with how to respond.

ABC News has learned the government is considering a number of new measures, including asking overseas airport authorities to increase security.

DIANE SAWYER, ABC ANCHOR: There is a new terror warning --

THOMAS: This threat was initially discovered near the beginning of the Sochi Winter Olympics, prompting warnings about toothpaste and cosmetic bombs that could be smuggled onboard planes. Sources tell us evidence continues to come in, indicating the bombmakers in Syria are still at work.

REP. MIKE ROGERS (R), MICHIGAN: This is exactly the kind of threat that keeps me up at night.

THOMAS: It's a potentially deadly convergence.

Al Qaeda bombmakers from Yemen have come to Syria at the same time thousands of foreign fighters, including many from Europe and some from the U.S., have arrived to join al Qaeda-inspired groups. The fear is that once the stealth bombs are designed, there's available manpower to carry out attacks with fighters carrying passports from Western countries that allow easy access to the U.S.

What's more, terrorists are flowing back and forth over Syria's porous border with Iraq. This week, after a classified intelligence briefing about Iraq, senators issued a warning.

SEN. LINDSAY GRAHAM (R), SOUTH CAROLINA: One thing I've learned from this briefing, our homeland is at risk.

SEN. MARCO RUBIO (R), FLORIDA: This is an urgent counterterrorism situation that our country faces.

THOMAS: Congressional leaders say it's an especially dangerous moment.

ROGERS: I've been on the Intelligence Committee for 10 years, chairman for the last four years. I have never seen a threat matrix so serious, so varied, and so many different streams of threat.