WASHINGTON -- International Monetary Fund Managing Director Kristalina Georgieva and other multilateral-organization leaders on Thursday urged countries with high COVID-19 vaccination rates to boost efforts to send doses to low- and middle-income countries.

Georgieva and the heads of the World Bank Group, World Health Organization and World Trade Organization expressed concern in a joint statement that it would not be possible to vaccinate at least 40% of the population in all countries by the end of 2021 without urgent action.

Wide disparities in vaccination rates in advanced economies and developing countries will be a key issue raised during a virtual global summit that the United States is organizing on the sidelines of the U.N. General Assembly.

IMF spokesman Gerry Rice told reporters on Thursday that President Joe Biden had invited Georgieva to speak at the Sept. 22 event, which has not yet been formally announced by the White House. A White House spokesman declined to comment.

Reuters reported this week that the United States was pushing global leaders to endorse an even more ambitious vaccination target at the summit: getting 70% of the world's population vaccinated by the time of the 2022 General Assembly.

The leaders said countries with high vaccination rates - which have collectively pre-purchased over 2 billion doses more than needed - should urgently swap their near-term delivery schedules with global distribution programs to help address gaps in low- and middle-income countries.

They urged high-income countries to fulfill their dose donation pledges and release vaccine companies from contracts so those doses can be delivered to people in need.

The group also urged vaccine manufacturers to prioritize and fulfill their contracts to COVAX and AVAT, an African distribution program, and improve transparency by sharing details on delivery schedules for all vaccine shipments.