UNITED NATIONS (AP) -- Many of the world's nations are gathering starting Monday in Spain for a high-level conference to tackle the growing gap between rich and poor nations and try to drum up trillions of dollars needed to close it. The United States, previously a major contributor, pulled its participation, so finding funding will be tough.

The four-day Financing for Development meeting in the southern city of Seville is taking place as many countries face escalating debt burdens, declining investments, decreasing international aid and increasing trade barriers.

The United Nations and Spain, the conference co-hosts, believe it is an opportunity to reverse the downward spiral, close the staggering $4 trillion annual financing gap to promote development, bring millions of people out of poverty and help achieve the U.N.'s wide-ranging and badly lagging Sustainable Development Goals for 2030.

U.N. Deputy Secretary-General Amina Mohammed said Wednesday that despite "the headwinds" and high geopolitical tensions, there is hope the world can address one of the most important global challenges -- ensuring all people have access to food, health care, education and water.

"This conference is an appeal to action," Spain's U.N. Ambassador Hector Gomez Hernandez said, "and we have the extraordinary opportunity to send a very strong message to defend the international community's commitment to multilateralism."

High-level delegations, including more than 70 world leaders, are expected in Seville, Mohammed said, along with several thousand others from international financial institutions, development banks, philanthropic organizations, the private sector and civil society.

At its last preparatory meeting on June 17, the United States rejected the 38-page outcome document that had been negotiated for months by the U.N.'s 193 member nations and announced its withdrawal from the process and from the Seville conference.

The rest of the countries then approved the document by consensus and sent it to Seville, where it is expected to be adopted by conference participants without changes. It will be known as the Seville Commitment -- or Compromiso de Sevilla in Spanish.

The document says the leaders and high-level representatives have decided to launch "an ambitious package of reforms and actions to close the financing gap with urgency," saying it is now estimated at $4 trillion a year.

Among the proposals and actions, it calls for minimum tax revenue of 15% of a country's gross domestic product to increase government resources, a tripling of lending by multilateral development banks, and scaling up private financing by providing incentives for investing in critical areas like infrastructure. It also calls for a number of reforms to help countries deal with rising debt.

U.N. trade chief Rebeca Grynspan told a news conference Friday that "development is going backward" and the global debt crisis has worsened.

Last year, 3.3 billion people were living in countries that pay more interest on their debts than they spend on health or education -- and the number will increase to 3.4 billion people this year, she said. And developing countries will pay $947 billion to service debts this year, up from $847 billion last year.

She spoke at a press conference where an expert group on debt appointed by U.N. Secretary-General Antonio Guterres presented 11 recommendations that they say can resolve the debt crisis, empower borrowing countries and create a fairer system.

While the U.S. objected to many actions in the outcome document, American diplomat Jonathan Shrier told the June 17 meeting: "Our commitment to international cooperation and long-term economic development remains steadfast."

He said, however, that the text "crosses many of our red lines," including interfering with the governance of international financial institutions, tripling the annual lending capacity of multilateral development banks and proposals envisioning a role for the U.N. in the global debt architecture.

Shrier also objected to proposals on trade, tax and innovation that are not in line with U.S. policy, as well as language on a U.N. framework convention on international tax cooperation.

The United States was the world's largest single funder of foreign aid. The Trump administration has dismantled its main aid agency, the U.S. Agency for International Development, while drastically slashing foreign assistance funding, calling it wasteful and contrary to the Republican president's agenda. Other Western donors also have cut back international aid.

The U.N.'s Mohammed said the U.S. withdrawal from the conference was "unfortunate," stressing that "many of the recommendations you see cannot be pursued without a continuous engagement with the U.S."

After Seville, "we will engage again with the U.S. and hope that we can make the case that they be part of the success of pulling millions of people out of poverty."