WASHINGTON — Calling Immigration and Customs Enforcement officials “American heroes,” Vice President Mike Pence doubled down on the Trump administration’s defense of the maligned agency on Friday and demanded that Democrats end their “irresponsible” push to disband it.

Mr. Pence, visiting the agency’s headquarters, said that to cede to activists and politicians’ calls to abolish it would jeopardize the country’s national security.

“So today, I want to make it clear to all of you and all of those looking on, under President Donald Trump, we will never abolish ICE,” Mr. Pence said. “And as the president said, we will never fail to applaud, and expand, and empower this agency with the resources that you deserve.”

ICE has been a source of mounting criticism among protesters, several Democratic politicians and even some of the agency’s investigators as the Trump administration’s “zero tolerance” immigration policy led to the separation of migrant families at the southwestern border. Though ICE officials were not responsible for the separations — which the president has ordered an end to and were conducted by Customs and Border Protection — some have come to see the agency as a representation of Mr. Trump’s aggressive approach to immigration enforcement.