Puerto Rico will receive humanitarian crisis relief from the poverty group Oxfam, which has slammed the Trump administration's "slow and inadequate" response to the unfolding crisis.

Oxfam International typically provides aid to the world's most impoverished regions but now says it will help Puerto Rico, a rare rebuke from the charity—and one that equates the U.S. response to that of a Third World or war-torn nation such as Syria or Bangladesh. 

"Oxfam rarely responds to humanitarian emergencies in the U.S. and other wealthy countries, but as the situation in Puerto Rico worsens and the federal government's response continues to falter, we have decided to step in," Oxfam America President Abby Maxman said in a statement.

Trump will visit the island Tuesday, though he reportedly won't formally ask Congress for relief funds until next month, weeks after the storm, compared with just days in the cases of Hurricanes Harvey and Irma. Maxman said that response left her "outraged" at the U.S. government's failure to address the most urgent needs of Puerto Ricans who remain without electricity and clean water.

The United States is considered a developed country with "more than enough resources" to mobilize an emergency response, despite failing to do so in a "swift and robust manner," Maxman said.

Hurricane Maria hit the island September 20, destroying homes and leaving Puerto Rican residents stranded without communication. The storm destroyed crops and storefronts in Puerto Rico. Secretary of Agriculture Carlos Flores Ortega estimated a $780 million loss in agriculture yields across the island, which already struggles with poverty. 

High winds and heavy rains washed out roads, bridges and other necessities. Fuel is in short supply, Maxman said, most people still lack access to clean water, and many hospitals are closed. Trump was heavily criticized for not waiving shipping restrictions to help get fuel and supplies to Puerto Rico, which the Department of Homeland Security deemed unnecessary because the island’s harbor infrastructure was too damaged to accommodate more shipping.

San Juan Mayor Carmen Yulín Cruz criticized Trump for not doing enough to help the 3.4 million Puerto Ricans affected by Hurricane Maria, which brought an attack from the president on Twitter.

"The mayor of San Juan, who was very complimentary only a few days ago, has been told by the Democrats that you must be nasty to Trump," Trump wrote on Twitter. "Such poor leadership ability by the mayor of San Juan, and others in Puerto Rico, who are not able to get their workers to help. They want everything to be done for them when it should be a community effort."

The death toll from Hurricane Maria in Puerto Rico remains unclear. The last official count recorded 16 deaths, but local reporters estimated at least 60 deaths. The humanitarian crisis is expected to claim hundreds of lives.

The White House did not immediately comment on the Oxfam aid.