The Open Arms charity says it is willing to defy Italian authorities and dock their migrant ship at Lampedusa.
The boat with about 100 migrants is stationed in the Mediterranean Sea off the Italian island, demanding permission to dock after 18 days at sea.
“We have exhausted physically, morally and technically the few resources that this organization has in this moment,” Open Arms founder Oscar Camps told Reuters on Monday.
Many of the migrants on board are sick, suicidal and close to mental breakdowns, the charity said.
The group has rejected offers from Spain to sail to one of its ports. France, Germany, Luxembourg, Portugal and Romania have offered to give the migrants refuge.
Under international law, a distressed ship is supposed to head to the first safe port. Open Arms says the ship and migrants could not withstand the journey to a Spanish port.
“While our boat is 800 meters off the coast of Lampedusa, European states are asking a small NGO like ours to face three days of sailing in harsh weather conditions,” the organization said.
While some onboard the rescue ship have been allowed to enter Lampedusa, Italy’s hard-line anti-immigrant Interior Minister Matteo Salvini is refusing to let the boat dock there.
He said Italy has done enough in accepting African migrants and is demanding other EU nations do more to help. He also called private charity migrant ships “taxis” for human traffickers.
Spanish Defense Minister Margarita Robles said what Salvini is doing is “a disgrace to humanity as a whole … putting human lives at risk for electoral reasons.”
A second ship, the Ocean Viking — operated by French charities Doctors Without Borders and SOS Mediterranean — is also at sea with 356 mainly Sudanese migrants looking for a safe port.
Lampedusa is the closest EU port from Libyan shores, where thousands of migrants looking to escape war and poverty try crossing the Mediterranean in search of safety, often aboard rickety vessels and flimsy rafts.
Those not rescued by charity ships are left to drown. Migrants picked up by the Libyan coast guard are returned to Libya and housed in migrant detention centers near Tripoli.
Some of those centers are caught in the fighting between rival Libyan governments.
Two missiles slammed into one detention center last month, killing 53.