Image copyright AFP Image caption UN Secretary-General Antonio Guterres said the cut would be 'devastating'

The US has been warned its decision to withdraw its support from the United Nations Population Fund will be a disaster for the world's most vulnerable families.

UN Secretary-General Antonio Guterres said it will have "devastating effects" for the health of women and girls.

In total, $32.5m (£26m) will be withdrawn for the 2017 financial year.

This is the first of the promised cuts to US financial contributions to the UN by the Trump administration.

The state department justified its decision by saying the Population Fund supports or participates in a programme of coercive abortion or involuntary sterilisation in China.

But the Population Fund, which promotes family planning in more than 150 countries, says this is an "erroneous claim", and that its work does not break any US laws.

On Tuesday, UN spokesman Stephane Dujarric said Mr Guterres deeply regretted their decision, adding he believed it was "based on an inaccurate perception of the nature and importance of the work done" by the fund.

Image copyright Getty Images Image caption The US Ambassador to the UN, Nikki Haley, is overseeing potential funding cuts to the body

Earlier this year, President Donald Trump reinstated a ban on US funding of any international organisation that provided any kind of abortion service or advice.

The state department referred to the presidential directive from January and a provision called the Kemp-Kasten Amendment in its statement on Monday.

What does the UN Population Fund do?

Help women and young people to access sexual and reproductive services, including family planning

Prevent unintended pregnancies and unsafe abortions

Support maternal health

Programmes in the world's "most fragile" countries, including Iraq, South Sudan, Syria, Yemen and Somalia

The UN Population Fund has often been the target of conservative Republican administrations, the BBC's Nada Tawfik in New York reports.

Presidents Ronald Reagan, George HW Bush and George W Bush withheld funding for the same reason.

The Population Fund, like other UN agencies, is funded by governments voluntarily. In 2015, it received $979m in donations, with the US being its fourth-largest donor.