The United Nations is at risk of "imminent financial collapse" due to member states not paying their fees, the body's head has warned.

António Guterres said the UN faced a financial crisis which was "deepening, threatening programme delivery", and that money could run out by July.

He wrote in a letter to all 193 member states that they had to honour their mandatory payments or overhaul the organisation's financial rules to avoid collapse.

It comes after the UN's largest contributor, the US, refused to contribute to its regular and peacekeeping budgets, and withdrew from several agencies it called a "waste of taxpayer dollars". Several other members are in arrears or are simply refusing to pay.

Though the UN General Assembly did approve a partial change to its financial system in late 2025, the organisation still faces a massive cash crisis compounded by a rule that means it is refunding money it never received.

At its headquarters in Geneva, signs warning of the situation have been put up everywhere. In an almost desperate attempt to save cash, the escalators are regularly turned off and the heating turned down.

Guterres wrote in his letter that the UN had faced financial crises in the past but that the current situation was "categorically different".

"Decisions not to honour assessed contributions that finance a significant share of the approved regular budget have now been formally announced," the secretary general said, without naming specific members.

He said the "integrity of the entire system" depended on states adhering to their obligation under the UN charter to pay their "assessed contributions" – adding that 77% of the total owed had been paid in 2025, leaving a record amount unpaid.

Guterres said a rule that the UN must return unspent money on particular programmes to members if it could not implement a budget created a "double blow" in which it was "expected to give back cash that does not exist".

"I cannot overstate the urgency of the situation we now face. We cannot execute budgets with uncollected funds, nor return funds we never received."

As a result, the UN is now returning millions of dollars it never actually had.

The letter reads: "Just this month, as part of the 2026 assessment, we were compelled to return $227m [£165m] – funds we have not collected."

"The bottom line is clear," Guterres wrote. "Either all member states honour their obligations to pay in full and on time – or member states must fundamentally overhaul our financial rules to prevent an imminent financial collapse."

UN agencies rarely get all the money they ask for to tackle humanitarian crises, but the past 12 months have been particularly difficult.

The US is the UN's largest contributor, but President Donald Trump has said it was not fulfilling its "great potential" and has criticised it for failing to support US-led peace efforts.

The US did not pay its contribution to the UN's regular budget in 2025 and offered only 30% of its expected funding to UN peacekeeping operations.

Then in January, Trump withdrew it from dozens of international organisations, including 31 UN agencies, to "end American taxpayer funding and involvement in entities that advance globalist agendas over US priorities".

In late December, the US pledged $2bn (£1.5bn) in funding for UN humanitarian programmes - warning the international organisation must "adapt or die" – a fraction of the $17bn it spent in 2022.

Other countries, such as the UK and Germany, have also announced significant reductions in foreign aid, which will inevitably impact the UN's work.

Guterres had warned earlier that same month that the UN faced its most fragile financial position in years – again citing unpaid fees – having said in October that it faced a "race to bankruptcy".

Trump has separately been accused by critics of seeking to replace some functions of the UN with his Board of Peace to oversee regeneration efforts in Gaza.

The US president has said its work would happen "in conjunction with the United Nations" - but when previously asked by a Fox TV journalist whether the board would take the UN's place, he replied: "Well, it might."

The US officially left the UN's World Health Organization last week. It had refused to pay its 2024 and 2025 dues despite, WHO lawyers say, being legally obliged to do so.

Other agencies are also making huge cuts.

The UN's human rights office has warned that serious violations will now go undocumented because it lacks the funds to deploy investigators. In the past, their evidence has led to prosecutions for war crimes and crimes against humanity.

In Afghanistan, which has one of the highest rates of maternal mortality in the world, UN Women has had to close mother and baby clinics. (BBC)

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