Vice President Joe Biden didn’t mention any names during his speech at the University of Denver Thursday, but his message was clear: the next president can’t be isolationist.

“The impulse to hunker down, shut the gates, build walls, withdraw is real,” Biden said.

But that’s a dangerous idea in the vice president’s view. And it’s an idea he says is being pushed by a “significant minority in both political parties.”

He didn’t mention Republican presidential nominee Donald Trump by name during his speech, but he said Americans are anxious about global engagement because politicians “exaggerate the threat and exacerbate people’s fears for their own political wellbeing.”

Biden went on to cast that approach as one that will lead to inevitable failure.

“The American people know in their gut that there is no existential threat to the U.S.,” Biden said.

He also pushed back on Trump’s narrative that the US military has been weakened.

“Clearly we are the strongest military in the history of the world. That is not hyperbole. This is the finest, best trained military in the history of the world,” Biden said. “That’s not why people respect us and race to come here. It’s because of our value system.”

Biden was the keynote speaker at an annual dinner for the Josef Korbel School of International Studies.

His hour-long talk touched on America’s foreign policy challenges, terrorism, U.S. wages and America’s perception abroad.

“American leadership is more respected and admired today than it was when we took office,” Biden said.

He pointed to things like rebuilding the U.S. economy, restoring relations with Cuba, efforts to close the detention facility at Guantanamo and outlawing of enhanced interrogation techniques.