US authorities are considering using ships to deport migrants, The New York Times reports.

The Trump administration is considering using ships, including a 500-foot (about 152 meters) training vessel and ferries, to deport migrants to Central and South America on journeys that could take days and cost millions of dollars, according to two US officials.

But such a plan has a number of risks, from the high cost of such transport compared to air transportation, to logistical complications and security issues.

At the same time, it remains unclear how the conditions for holding the migrants will be carried out.

The plan could, however, offload some deportation costs from US Homeland Security to the Defense Department.

The discussions over recent weeks are still preliminary, but officials have identified possible ships, including the Training Ship Golden Bear, a US maritime academy vessel docked in California, said one person who spoke on the condition of anonymity because of the sensitivity of the plan. US Defense Department officials have also reached out to companies about ships in Europe, the official said.