Disruption to supplies coming through the embattled Red Sea port of Hodeida could "cause starvation on an unprecedented scale," the British based NGO said in a new report.
Save the Children said an extra one million children now risk falling into famine as prices of food and transportation rise, bringing the total to 5.2 million.
Any type of closure at the port "would put the lives of hundreds of thousands of children in immediate danger while pushing millions more into famine," it added.
Impoverished Yemen has been mired in deadly conflict between Shiite Huthi rebels and troops loyal to President Abedrabbo Mansour Hadi since 2014.
A Saudi-led alliance intervened in 2015 in a bid to bolster the president, accusing Iran of backing the Huthis, but nearly 10,000 people have since been killed.
Deadly clashes resumed around the Huthi-held port city of Hodeida following the collapse of talks in Geneva earlier this month.
"Millions of children don't know when or if their next meal will come," said Helle Thorning-Schmidt, CEO of Save the Children International.
"In one hospital I visited in north Yemen, the babies were too weak to cry, their bodies exhausted by hunger.
"This war risks killing an entire generation of Yemen's children who face multiple threats, from bombs to hunger to preventable diseases like cholera," she added.
The United Nations has warned that any major fighting in Hodeida could halt food distributions to eight million Yemenis dependent on them for survival.
Saudi Arabia and its allies accuse the Huthi rebels of smuggling arms from Iran through Hodeida and has imposed a partial blockade on the port.
The Huthis and Iran both deny the charges.
Published : September 18, 2018
By : Agence France-Presse London