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A newly launched online campaign called Yemen Can't Wait saw some 350 public figures sign an open letter urging the United States, Britain and France to do more to end a war that has claimed more than 10,000 lives in just 1,000 days.

The conflict "has transformed the poorest country in the Middle East into the world's worst humanitarian crisis," said the letter published in France's Le Monde daily on Monday.

The letter calls on US President Donald Trump, his French counterpart Emmanuel Macron and British premier Theresa May to push for an immediate ceasefire and peace talks as permanent members of the UN Security Council. 

It pointed to these countries' lucrative arms contracts with Saudi Arabia, which is determined to crush the rebels it sees as proxies for arch-rival Iran.

"Millions of Yemeni women, men and children feel abandoned by world leaders, who seem to place profits and politics before human lives," said the letter signed by stars including actors Bill Nighy and Juliette Binoche.

Millions of Yemeni women, men and children feel abandoned by world leaders, who seem to place profits and politics before human lives

Photographs of children starving to death have failed to spur the international community into ending the world's worst humanitarian crisis, which charities warn is deepening by the day.

"Yemen is regarded as an invisible conflict, that the world has forgotten," Liny Suharlim, ACTED's Yemen country director said.

At the top of many aid workers' wish list is to see the Saudi-led coalition, which has been pounding Houthi rebels since March 26, 2015, lift the blockade that has drastically reduced their ability to bring in food and medical supplies.

Caroline Anning, a senior adviser at Save the Children who recently travelled to Yemen, suggested Saudi Arabia's success in keeping journalists away helped explain the conflict's failure to seize the world's conscience.

But she added that the fact that the war has not sparked a significant refugee crisis – a combined result of poverty, geography and Yemenis' inability to escape the relentless fighting – has also encouraged the West to ignore the conflict.

"There isn't a big refugee outflow that's impacting other countries," she said.

"For all of the suffering with the extreme rates of acute malnutrition, the number of children dying every day, the world's biggest cholera outbreak or from hunger, it's contained within Yemen's borders."

In a country which was highly dependent on food imports even before the war, aid groups estimate that some 22 million Yemenis – three quarters of the population – now rely on aid to survive.

Humanitarian workers say the Saudi blockade, tightened after a missile attack on Riyadh in November, has exacerbated disease which was already rampant in Yemen by creating a dire vaccine shortage.  

Some aid supplies have been allowed in, but the blockade has had knock-on effects including soaring fuel prices which are crippling everything from hospitals to water plants.

"There are things that could happen tomorrow that could stop children from dying," Anning said.

"Considering the depth of the suffering and the fact that it's entirely man-made, we haven't had the level of international attention on Yemen that you would expect to see."

Agencies contributed to this report