The secretary general of the United Nations said Thursday that its cash supply had been severely depleted because of what he described as delayed contributions by many member states, and he warned the organization’s employees that they must find ways to cut expenses.

“Our cash flow has never been this low so early in the calendar year, and the broader trend is also concerning,” Secretary General António Guterres said in an internal memorandum to employees shared with The New York Times. “We are running out of cash sooner and staying in the red longer.”

According to a tally known as the “honor roll” on the United Nations website, 112 of the organization’s 193 members have paid their annual assessments in full.

The United States, by far the biggest single contributor at 22 percent of the budget, has not yet paid, but diplomats said the Americans typically completed their payments toward the end of the year.

Mr. Guterres did not single out any particular country among the 81 that had not yet paid, and he acknowledged that countries followed different fiscal calendars.

Nonetheless, he said, “this new cash shortfall is unlike those we have experienced previously.”

It is not unusual that so many members have yet to pay their assessments. By this time last year, 77 had not yet paid. In July 2016, 95 had not yet paid.

Assessments to fund the budget are based on a formula tied to each member’s ability to pay, which takes into account national income, population and debt levels, among other factors. United Nations peacekeeping operations are funded by a budget that is calculated separately.

Under Article 19 of the United Nations Charter, if a member is in arrears in an amount that equals or exceeds the assessment due for the previous two years, that member could forfeit its General Assembly vote unless there are extenuating circumstances.

Currently five members are subject to Article 19: Comoros, Guinea-Bissau, São Tomé and Principe, Somalia and Libya. But only Libya has lost its vote.

Mr. Guterres said in the memorandum that he had appealed to those members who had not yet paid their annual assessments to do so “on time and in full,” and that he had “highlighted the risk the current situation poses to the delivery of mandates and to the reputation of our organization.”

He did not specify precisely how the organization would conserve its cash, but he said that “for our part, we will need to take measures to reduce expenses, with a focus on nonstaff costs.”

As word of the memorandum quickly spread on Thursday, Mr. Guterres’s aides sought to dispel any notion that the United Nations was in a dire fiscal emergency.

“We are not trying to alarm,” Stéphane Dujarric, the secretary general’s spokesman, told reporters at a daily briefing. He said Mr. Guterres’s memo was a reminder to the member states that “we don’t have the same flexibility as governments in terms of controlling income and the timing of income.”

The reminder came against a backdrop of pressure on the United Nations to control its expenses, which has been led by the American ambassador, Nikki R. Haley.

After the budget committee of the General Assembly agreed last December to a $5.4 billion budget for 2018-2019, Ms. Haley took credit for a $285 million cut from the previous budget.

“The inefficiency and overspending of the United Nations are well known,” she said at the time. “We will no longer let the generosity of the American people be taken advantage of or remain unchecked. (NYTimes)

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