WASHINGTON — Secretary of State Mike Pompeo accused Cuba and Russia on Monday of propping up President Nicolás Maduro of Venezuela in the Trump administration’s most explicit argument yet that his government is a dictatorial regime kept alive by two American adversaries.

Mr. Pompeo’s comments came amid a devastating power outage that has plunged many of Venezuela’s most populous areas into darkness, spoiling food in a nation where little is available.

He denied Mr. Maduro’s accusation that foreign powers — a clear reference to the United States — had any role in creating the blackout that has brought the country to the brink of social implosion. Instead, Mr. Pompeo said, the blame lies squarely with Havana and Moscow.

“When there is no electricity, thank the marvels of modern Cuban-led engineering,” Mr. Pompeo said in comments laced with sarcasm. “When there’s no water, thank the excellent hydrologists from Cuba. When there’s no food, thank the Cuban communist overlords.”