By Alex Kirby BBC News Online environment correspondent

The head of the United Nations Population Fund (UNFPA), Dr Thoraya Obaid, says war on Iraq would be catastrophic.

She said a recent warning that a conflict would "open the gates of hell" was absolutely right.

Dr Obaid said the only way to fight terrorism was to tackle the causes of injustice.

What the US decision will do is increase maternal mortality and worsen the HIV/Aids crisis

Dr Thoraya Obaid

She said the US decision to withhold funding from UNFPA would worsen the HIV/Aids crisis.

Dr Obaid was speaking in a BBC News Online interview after taking part in a two-day meeting in Canterbury, UK, of the World Faiths Development Dialogue (WFDD).

The meeting, chaired by the Archbishop of Canterbury, Dr George Carey, and the World Bank president, James Wolfensohn, involved participants from many religions, including Muslims, Jews, Christians, Sikhs, Buddhists, Hindus and Bahais.

Hope to the hopeless

Dr Obaid, UNFPA's executive director, was born in Baghdad, but is a Saudi citizen.

She told BBC News Online: "Amr Moussa, the head of the Arab League, said last month that war against Iraq would 'open the gates of hell' in the Middle East, with instability across the region.

Faiths met in Canterbury

"He was right. Nobody wants war, and I pray that this one will be averted, because if it breaks out it will destroy people, lives and futures.

"To fight terrorism you have to fight the root causes of injustice - poverty, disease, joblessness. Nobody can live without hope.

"If by 2015 we can realise the Millennium Development Goals, which aim to halve global poverty, then we'll be turning our faces against injustice."

Punished by association

Earlier this year the US announced that it was withholding $34m in funding for UNFPA, because, it claimed, the agency was helping China to enforce a one-child policy and encouraging abortions among Chinese women.

Dr Obaid told BBC News Online: "That's 12% of our total funding. It really is a crisis for us.

Dr Thoraya Obaid: "Fight injustice, not war"

"We have nothing to do with abortion at all. So our other programmes are now going to suffer because of an issue we don't even touch.

"What the US decision will do is increase maternal mortality and worsen the HIV/Aids crisis.

"We're still hoping to find a way around it, and we're talking to the State Department in Washington. But so far we haven't succeeded."

Crossing the faith boundaries

Dr Obaid said the Canterbury meeting had been "a very harmonious and elevating experience. I felt both spiritually and intellectually elevated by it."

She said: "In many communities, 50-60% of health and education services are provided by faith-based organisations, so there's great potential there.

"Life-and-death issues sometimes force change upon you - look at what the Christian churches are doing in Africa about HIV/Aids."

The Canterbury agenda devoted one session to discussing how to tackle HIV/Aids, which the agenda described as "the critical development challenge in today's world".