Chinese President Xi Jinping on Saturday pledged $2 billion for a new development fund for poor countries on a UN visit showcasing Beijing's growing global role.

Xi's announcement, made in his first address to the United Nations, follows longstanding criticism from the United States and other developed countries that China has not taken responsibilities in line with its aspirations for a greater global role.

The speech is the latest high-profile move for Xi on a trip that has included a White House state visit and will see him chair a UN forum on women's rights on Sunday.

Addressing a UN summit on development, Xi said China would act "by putting justice before interests and joining other countries in a concerted effort to realize the post-2015 agenda."

Xi said that China would launch an assistance fund for developing countries with an initial investment of $2 billion.

The Chinese leader said that his country would step up investment in the least developed countries -- which are mostly in Africa -- by at least $12 billion by 2030.

China has been an increasingly active investor around the world, although it has generally focused on seeking resources rather than broader humanitarian goals.

Xi said that China would also relieve debts owed by least developed countries this year. He did not provide a figure on the debts or say which countries would be affected.

The United Nations on Friday set a goal of ending extreme poverty by 2030, an effort that the global body says could require up to $5 trillion a year.

- Send tourists -

After his speech, the Chinese president hosted a meeting on South-South cooperation attended by more than a dozen leaders eager to present their wish lists.

Ugandan President Yoweri Museveni urged Xi to encourage Chinese companies to invest in Africa and to open up the Chinese market to African goods as the best way to promote economic development.

He then added a third, concrete request.

"Tourists. If you could send me just two million of those, I'll be very happy," said the Ugandan leader, drawing applause.

In January, Xi promised $250 billion in investment over 10 years in Latin America, which the United States has long considered its sphere of influence.

China's economy has soared over the past 15 years to become the world's second largest after the United States, although concerns have been rising in recent months over the country's financial markets and long-term growth.

China has increasingly taken an assertive role in the world, especially in myriad disputes with its neighbors, but retains little stake in the World Bank and International Monetary Fund.

With a reform plan for the Washington-based institutions blocked by US Republican lawmakers, China has set up its own lender, the Asian Infrastructure Investment Bank.

The bank, which Xi reaffirmed would open soon, has widely been seen as a way for China to dilute the influence of the United States and Japan, the most prominent holdouts from the new lender.

"It is important to improve global economic governance, increase the representation and voice of developing countries and give all countries equal right to participating in international rule-making," Xi said.

- Easing concerns -

China's aid commitment remains far below levels of Western countries.

The United States in 2013 provided more than $30 billion, and Britain, France, Germany and Japan all gave more than $11 billion, according to the Paris-based Organization for Economic Cooperation and Development.

Xi called on developed countries to remain "the main channel" for assistance to poor nations.

The pledge nonetheless marks the second day in a row in which China has addressed one of many concerns of Western countries.

On his visit Friday to Washington, Xi pledged action on climate change. China is the largest emitter of carbon blamed for the world's rising temperatures.

China promised $3.1 billion to help developing countries adapt to climate change and said it would set up a "cap-and-trade" system to limit emissions.