Mark Green, the head of USAID, pictured here in August at his Washington office, announced more than $800 million in new humanitarian aid to Africa and the Middle East this week at the U.N. General Assembly. (Bill O'Leary/The Washington Post)

A search-and-rescue team from Los Angeles comprising 67 people, five dogs and 62 tons of excavating equipment arrived in Mexico City on Thursday morning to help locate survivors of the recent earthquake.

They are the sixth disaster assistance response team currently dispatched by the U.S. Agency for International Development to countries struck by disasters, both natural and man-made.

"America is and will remain the world's leading humanitarian donor," Mark Green, the head of USAID, said in announcing the response team's arrival in Mexico. "Whether it's responding to an earthquake, drought or conflict, America is committed to standing shoulder to shoulder with people in their hour of need. It is who we are as Americans."

Green has been driving home that point repeatedly at the U.N. General Assembly this week.

Many have questioned the Trump administration’s commitment to foreign aid, including emergency humanitarian assistance.

The administration's proposed budget shows deep cuts in foreign aid. There is bipartisan support for many of the programs in Congress, however, and much of the assistance has been restored by appropriations committees. But doubts persist that enough money will be made available at a time of overwhelming need.

“We’re still concerned,” said Carolyn Miles, head of Save the Children, which says the United States has not lived up to a commitment made by the Obama administration at last year’s General Assembly to provide education for refugee children in the Middle East. “Congress is pushing back, but we don’t have the budget yet.”

“We’ve seen two major earthquakes, three hurricanes and flooding in India, Bangladesh and Nepal, not to mention the Rohingya,” she said, referring to the refu­gee crisis in Burma, also known as Myanmar. “The number of significant emergencies is unprecedented. The leadership of the United States is important.”

This week, Green announced more than $800 million in humanitarian aid to Africa and the Middle East. All of it is new money, although some will not be handed out immediately but carried over from the current fiscal year and prioritized in the next year.

The biggest chunk, $575 million, is to provide food in four countries with emerging famines — Yemen, South Sudan, Nigeria and Somalia.

On Wednesday, Green announced $264 million in aid for Iraq. Some will be spent on immediate needs, such as food, hygiene kits and emergency shelters. But some will help families prepare to return home after their villages have been liberated from the Islamic State.

Green’s mantra is that all aid programs should aspire to go out of business, his shorthand way of saying he prefers aid that helps needy countries develop their economies and spur good governance so they are better prepared to deal with calamities.

“So we are working to deal with immediate needs, and we’re working to deal with the kinds of long-term challenges that I think have made these among the most vulnerable people in society,” he said.

But a big part of his message this week has been that the United States expects other countries to chip in more, too. In raw numbers, the United States spends more money on humanitarian aid than any other country. But as a percentage of the economy, the United States is in the same ballpark as countries such as Portugal and Japan, while many European countries like Sweden, Switzerland and Luxembourg are far more generous.

“We are talking to partners about their contributions,” Green said, “making it clear that [while] we believe in the leadership role that we play in humanitarian assistance, we want others to join us — we expect others to join us.”

But the emergency needs keep mounting. Only once before have so many disaster response teams been deployed around the world, in 2015. Now there are teams in the Caribbean, South Sudan, Iraq, Syria and Nigeria as well as Mexico.

Green, who has a background in development, has said one of the first things that struck him when he arrived at USAID two months ago was the overwhelming need for immediate help.

"And we're seeing right now a time in history where the world's on fire, and there are immediate, pressing humanitarian needs that we see right before us," he said Thursday.