Sunday on ABC’s “This Week,” former Obama HUD Secretary Julián Castro warned that “the greatest threat to our national security” was President Donald Trump “damaging” America’s relationships with foreign countries.

Partial transcript as follows:

STEPHANOPOULOS: You laid out your experience. One thing you don’t have is foreign policy experience. What do you see now as the greatest threat to our national security today and what qualifies you to take it on?

CASTRO: Well, I—I believe that today the greatest threat to our national security is the fact that this president, as one of your previous guests has said, is damaging the relationships that we’ve had in place in the post-World War II era, whether it’s NATO or other alliances with individual countries, that have kept us safer. The first thing that I would do if I were president, with regard to our relationships around the world, is to strengthen them. Because those alliances have helped keep us safe. It’s also true that today being—being the strongest country, being the safest country, I think requires more diplomatic efforts than ever.