The charity warned that the war was disrupting key air, sea and land routes, with dire ripple effects on global aid supplies.

Since US-Israeli forces launched the war against Iran on February 28, Tehran has responded with attacks throughout the Middle East and threats that have nearly halted shipping in the Strait of Hormuz, through which one-fifth of global oil supplies normally passes.

Aid deliveries have been heavily impacted, with shipping costs soaring up to 50 percent in some cases as the shipments are rerouted, Save the Children said.

This has left lifesaving aid intended for at least 410,000 children and their families in crisis-ravaged Sudan, Afghanistan and Yemen stuck in the Middle East.

"The escalating conflict is having grave ripple effects for children far beyond the region," Willem Zuidema, the NGO's head of global supply chains, said in a statement.

One shipment of medical supplies bound for Sudan is stuck in Dubai due to the closure of the Strait of Hormuz, the charity said. This was putting more than 90 primary health care facilities across Sudan at risk of running out of essential medicines, it added.

Those medical supplies included antibiotics, antimalarials, deworming treatments and pain and fever medicines intended to support over 400,000 children in Sudan, it said.

The charity said it was exploring alternative routes to Sudan, including by road across Saudi Arabia to Jeddah and then by sea to Port Sudan.

This, it warned "could add US$1,000-$2,000 per container in costs".

- 'Grave ramifications' -

Critical nutrition supplies intended to support 5,000 children and 1,400 pregnant and breastfeeding women in Afghanistan had also been impacted, Save the Children said.

That aid had been meant to be shipped from India via Iran, but will now have to be flown in, "at a cost over over $240,000 -- more than the value of the supplies", it said.

The charity said it also had a shipment of medicines, including antibiotics, for around 5,000 children in Yemen, which remained stuck in Dubai.

"For the first time ever, Save the Children will transport these supplies via road, doubling the transport cost," it said.

Zuidema called on all parties to the conflict to "facilitate the safe passage of humanitarian assistance to children".

"There should be no barriers to life-saving supplies: exemptions should be put in place to allow humanitarian supplies, fertiliser, and food to be able to move through the Strait of Hormuz," he said.

"With global humanitarian needs already at record levels, further escalation of the conflict in the Middle East and wider region will have grave ramifications for crises across the world."