While the president did not specify what precisely he plans to do with the island nation, he has frequently said he believes the government in Havana, facing a severe economic crisis, is on the verge of collapse.
His administration has opened up negotiations with elements of Cuba's leadership in recent weeks, while Trump himself has hinted that kinetic action could be possible.
"I built this great military. I said, 'You'll never have to use it.' But sometimes you have to use it. And Cuba is next, by the way," Trump told the conference on Friday.
"But pretend I didn't say that. Pretend I didn't.
"Please, please, please, media, disregard that statement. Cuba's next."
Cuban President Miguel Diaz-Canel has acknowledged that the country is in talks with the United States in a bid to avert potential military confrontation.
Cuba's economy has been battered by disruptions in oil imports, which it relies on to run power plants and transportation.
Prior to the US operation to capture now-deposed Venezuelan leader Nicolas Maduro in January, Venezuela had provided much of Cuba's oil needs, but Caracas' new government, under pressure from Washington, has ended those shipments.
Earlier in March, Trump had said Cuba may be subject to a "friendly takeover," before adding: "It may not be a friendly takeover."
