The U.N. humanitarian chief is warning that the fight against famine is being lost in Yemen, which is already facing the world's worst humanitarian crisis with 75 percent of its 29 million people in need of assistance.

Mark Lowcock told the Security Council on Friday that the situation "has deteriorated in an alarming way in recent weeks."

He says the situation is "bleak," adding: "We may now be approaching a tipping point, beyond which it will be impossible to prevent massive loss of life as a result of widespread famine across the country."

In this Aug. 25, 2018 image made from video, severely malnourished infant Zahra is bathed by her mother, in Aslam, Hajjah, Yemen. Yemen’s civil war has wrecked the impoverished country’s already fragile ability to feed its population. Around 2.9 million women and children are acutely malnourished; another 400,000 children are fighting for their lives only a step away from starvation. (AP PhotoHammadi Issa)

In this Aug. 25, 2018 image made from video, severely malnourished infant Zahra is bathed by her mother, in Aslam, Hajjah, Yemen. Yemen’s civil war has wrecked the impoverished country’s already fragile ability to feed its population. Around 2.9 million women and children are acutely malnourished; another 400,000 children are fighting for their lives only a step away from starvation. (AP PhotoHammadi Issa)

Lowcock says two recent developments threaten to overwhelm the aid operation — a serious economic deterioration that has reduced the value of Yemen's currency by some 30 percent and intensified fighting around the key port of Hodeida.