Cuba's ambassador to Haiti and five Cuban doctors made a courtesy call Friday to a US Navy hospital ship anchored off Port-au-Prince, in a sign of warming ties between Havana and Washington.

US doctors aboard the USNS Comfort, which is on its fourth humanitarian mission to Haiti, will see patients from the capital and perform surgeries through September 18.

Cuban Ambassador Ricardo Garcia Napoles said that he received the invitation to come aboard the USNS Comfort "with great pleasure."

This is "a historic visit in the context of the renewal of diplomatic relations between Cuba and the United States," he said.

The United States and Cuba reestablished diplomatic ties earlier this year, following a five-decade freeze.

The US envoy to Haiti, Pamela White, also hailed the visit at a ceremony launching the ship's latest mission.

"I never thought I would see the day that I could recognize the Cuban ambassador at an official event and I'm so happy," she said.

The US military uses ships such as the USNS Comfort to provide vital assistance to Caribbean countries, including the Americas' poorest nation, Haiti, which is still recovering from a deadly 2010 earthquake.

The 1,000-foot (300-meter) vessel provided more than two months of medical assistance following the quake, which killed more than 250,000 people and crippled the nation's infrastructure.

Cuba also has a long-standing tradition of rendering medical aid in Haiti.

A total of 700 Cuban doctors currently work in Haiti, while more than 800 Haitian doctors have completed their medical training on the communist island.