With record numbers of people fleeing trouble in their homelands, the Obama administration is struggling to confront what Secretary of State John F. Kerry on Monday described as a “global humanitarian crisis, in some places a catastrophe.”

The scale of that emergency has intensified dramatically over the past decade, with an estimated 65.3 million people forcibly displaced by war, sectarian conflict and persecution in 2015, up from 37.5 million in 2005, according to the U.N. Commission on Human Rights.

On Tuesday, President Obama will convene a special summit here on the sidelines of the U.N. General Assembly aimed at rallying global support for the victims of the worst refugee crisis since World War II.

Obama is expected to announce new commitments from world leaders and business executives to help relocate and provide economic aid to refugees — including a vow to welcome 110,000 into the United States next year, a 30 percent increase from 2016.

But critics said the summit also highlights Obama’s failings on the issue, including his refusal to use U.S. military power to carve out safe areas for those fleeing the Syrian government’s barrel bombs and artillery attacks.

The war between President Bashar al-Assad’s regime and an array of rebel forces, including the Islamic State, has produced an exodus of 4.8 million Syrians, many of whom have massed in Turkey and spread into Europe.

“The bitter truth is this summit was called because we have been largely failing — failing the long-suffering people of Syria in not ending the war in its infancy,” Zeid Ra’ad al-Hussein, the United Nations’ human rights chief, said Monday as world leaders gathered in New York.

Images of injured and dead children have highlighted the humanitarian disaster in Syria, but rising strains of nationalism in Europe and the United States have blunted appeals from human rights advocates for the admittance of a greater number of refugees.

The Obama administration announced in August that it had met its goal of welcoming 10,000 Syrians this year, a number that officials said is expected to rise in 2017. Yet Republican presidential nominee Donald Trump has cited terrorism fears in his call for a temporary ban on Muslim refugees from Syria and elsewhere.

Over the past year, Obama has tried with increasing urgency to counter Trump, lambasting his proposals as contrary to American values and counterproductive to fighting terror.

This year, the United States had accepted 28,957 Muslim refugees through early August, the highest number since data on religious affiliation became available in 2002, according to an analysis from the Pew Research Center.

But the bombing attacks that injured 29 in New York and New Jersey over the weekend underscored Obama’s challenge in calming public anxiety. The initial police investigation focused on a 28-year-old Afghan immigrant, and the president urged the public not to “succumb to that fear.”

Terrorists, Obama said in a brief public statement, “want to inspire fear in all of us, and disrupt the way we live, to undermine our values.”

Human rights advocates praised the president’s summit, calling it a small first step in a process that will require sustained, long-term engagement from the United States and other nations.

Of the world’s estimated 65 million refugees, 41 million have fled their homes but remained in their own nations, and 21 million have fled their countries, the U.N. report found. An additional 3 million are awaiting decisions on asylum.

Obama’s efforts are “still just a tiny drop in the bucket,” said Margaret Huang, interim executive director of Amnesty International. “The United States does accept more refugees than any other country in the world, and there are reasons for this administration to be proud of its record. . . . But it’s not enough.”

The U.N. summit will seek to address a crisis that goes well beyond Syria and the broader Middle East. Most refugees today are trapped in camps in relatively poor nations such as Thailand, Jordan, Kenya and Pakistan. Burma and Congo have sent the most refugees to the United States this year, followed by Syria and Iraq.

In all, eight countries host more than half the world’s refugees, and 75 percent of the U.N. budget for migrants and refugees comes from 10 nations, according to the world body.

“We need to give them basic succor,” said Michel Gabaudan, president of Refugees International, an aid group based in Washington. “And the money has not matched the rise in need.”

Nor has the political will. In Germany, Chancellor Angela Merkel’s decision to accept tens of thousands of Syrians last year prompted massive protests. On Sunday, her ruling coalition suffered major losses in the Berlin state election to the far-right opposition party that campaigned on an anti-immigrant platform.

In Hungary, public polling has shown that voters are likely to reject a refu­gee quota mandated by the European Union in a national referendum early next month.

“People around the world are frightened by things they see happen, acts by extremists, but it’s very important to understand refugees are not the perpetrators of this kind of violence,” said Chris Boian, spokesman for the U.N. refugee agency. “They’re fleeing that same violence.”

In the United States, a bipartisan coalition in the House, including 47 Democrats, approved a bill in November that would require stringent new screening procedures for Syrian and Iraqi refugees. That same month, Obama toured a Malaysian refu­gee center during a trip to Asia, kneeling on the floor to chat with schoolchildren.

“The notion that somehow we would be fearful of them, that our politics would somehow leave us to turn our sights away from their plight, is not representative of the best of who we are,” Obama said then.

The House legislation, opposed by the White House, was defeated in the Senate.

Yet human rights advocates have criticized the administration for not doing more to resettle the tens of thousands of children fleeing violence in Central America who have illegally crossed into the United States from Mexico in recent years.

The Obama administration has said those migrants are subject to deportation if they fail to qualify for political asylum. Under pressure from advocates, the administration expanded a refu­gee program for the Central American minors in July, but only a few thousand have been granted refu­gee status.

“It’s a massive failure on the Obama administration’s part to not deal with this issue,” Huang said.

Nakamura reported from Washington. Carol Morello in New York contributed to this report.