UN High Commissioner for Refugees Filippo Grandi met US Secretary of State Rex Tillerson on Sunday and warned that American funding is "vital" to his mission to help victims of the world's wars.

The pair met at Tillerson's hotel in New York ahead of the United Nations General Assembly, where officials are to debate US demands for reform to the world body's budget -- including cuts to Washington's contributions.

The United States, which makes large voluntary contributions to some UN missions alongside its formal dues to the organization, is seeking savings, but Grandi warned that this is not the time to cut refugee money.

At a photo opportunity with Tillerson, he was asked whether the UNHCR could continue to meet its current workload without US funding, he said: "I would say no."

"US aid is vital to what we do to support refugees around the world and to find solutions to their situations," he added, before reporters were ushered out and the pair began their meeting.

The UN refugee agency relies almost entirely on voluntary contributions to fund its programs worldwide.

Last year, the United States was the number one contributor, providing $1.5 billion to the $4 billion annual budget.

The United Nations is struggling to cope with the biggest refugee crisis since World War II, with 65 million people on the move.

Source: AFP