A dozen Venezuelan doctors volunteered to join the USNS Comfort as the Navy hospital ship visits three South American countries that are struggling to cope with a flood of migrants from crisis-wracked Venezuela.

The doctors all live in the United States, but they wanted to help fellow Venezuelans who have fled widespread shortages of food and medicine amid an economic collapse that has pushed millions of people into poverty.

"This is like a Band-Aid" that will provide only temporary relief, said Dr. Marco Bologna, a cardiologist who now lives in Florida, where he is a member of the Venezuelan American Medical Association. "But it is the right thing to do and it helps us to do something for our country."

The Comfort has been described as a threat by Venezuela's socialist government and it will not visit that country during its 11-week tour of Latin America. The ship sailed from Norfolk, Virginia, on Thursday.

It will spend several days at two Colombian ports , one of which is just a one-hour drive from the border with Venezuela. The ship will also dock at ports in Ecuador and Peru, two other nations that are now home to hundreds of thousands of struggling Venezuelans. It will wrap up its tour in the Central American country of Honduras.

U.S. officials said the itinerary was designed with several local needs in mind, including the plight of Venezuelan migrants who are desperately seeking health care. A report published this month by a group of Venezuelan civil society groups estimated 20,000 doctors have left Venezuela since 2012.

"Each of the countries that we will spot was closely consulted. We have worked closely with them to ensure that we are providing the right care, at the right time, and at the right locations," said Coast Guard Rear Adm. Steven Poullin, director of operations at the U.S. Southern Command. "Obviously one of the factors that we considered was the Venezuelan crisis and the opportunity to treat Venezuelan migrants."

According to the United Nations, 1.9 million Venezuelans have left their country since 2015. The most recent migrants have little money for transport and many have been trying to reach their destinations on foot, in perilous journeys that can take several weeks.

The Venezuelan American Medical Association said it has been working with the Southern Command for several months to prepare the mission. It said more than 1,000 civilian doctors applied to serve on the ship, but there were spots for only a dozen volunteers on board the vessel, whose crew of 300 is made up mostly of Navy personnel.

One of the applicants who got left out was Gabriel Pinedo, a Venezuelan doctor who now delivers mail in Orlando, Florida, because he hasn't been able to have his degree validated in the United States.

Pinedo said he is currently applying for asylum in the U.S. and his lawyer told him that it would not be wise to leave the country. "It is frustrating not to be able to go," he said. "I already saw myself there."

The Comfort is equipped to attend to 750 patients a day during its South American journey and doctors on the ship will be able to perform 20 surgeries a day.

The ship's visit to South America comes just weeks after the U.S. put financial sanctions on Venezuelan President Nicolas Maduro's wife. President Donald Trump has described Maduro as a dictator and said that "all options" are on the table when it comes to restoring democracy in Venezuela, including military intervention.

Venezuela's government allowed a Chinese hospital ship to visit the country in September, but it has refused humanitarian aid from Western countries, arguing that such offers are just ploys for meddling in the country's affairs.

The Venezuelan doctors on the Comfort said they would like to see officials open a "humanitarian channel" that would allow medicine and food to be delivered into the country regularly.

"What we are doing here has a limited scope," said Dr. Rafael Gottenger, a plastic surgeon on the mission. "But it is good to be able to help your people."