By May Angel and Tristan Veyet

LONDON, March 16 (Reuters) - As the U.S.-Israel war with Iran enters its third week, analysts warn it is severely disrupting fertiliser markets and endangering food security for developing countries in the near term.

Here is how the conflict is affecting fertiliser costs, trade flows and output:

WHY IS THE HORMUZ STRAIT KEY FOR FERTILISER SUPPLY?

Fertiliser production is energy-intensive, relying heavily on natural gas as a feedstock, with energy making up as much as 70% of production costs.

From sea turtles to birds and the gentle dugong, the Persian Gulf's diverse but fragile marine life is threatened by the bombs and oil of the war in the Middle East.

The ecosystem was already under pressure from climate change and maritime traffic before the United States and Israel launched their war on Iran at the end of February, leading to Tehran's region-wide retaliation.

WARSAW, March 17 (Reuters) - Poland will not send troops to Iran as the conflict does not directly affect its security, Prime Minister Donald Tusk said on Tuesday, adding that the United States and other powers understood Warsaw's decision.

U.S. President Donald Trump called on allies over the weekend to help secure the Strait of Hormuz as Iranian forces continue attacks on the vital waterway amid the U.S.-Israeli war on Iran, now in its ​third week.

WASHINGTON, March 17 (Reuters) - The Trump administration is seeking other sources of fertilizer amid the ongoing Iran war's shipping constraints, including from Venezuela and possibly Morocco, White House economic adviser Kevin Hassett said on Tuesday.

"We've ... established licenses for Venezuela to produce more fertilizer. We've had discussions with Morocco," he said on CNBC's "Squawk Box" program, calling it "an insurance policy against disruption" for U.S. farmers.

By Olivia Le Poidevin

GENEVA, March 17 (Reuters) - Israeli airstrikes on residential buildings, displaced people and healthcare workers in Lebanon raise concerns under international law and may amount to war crimes, the United Nations human rights office said on Tuesday.

The Israeli military has been carrying out airstrikes in Lebanon since the Iran-backed Shi'ite Muslim group Hezbollah fired rockets at Israel from Lebanon early in the U.S.-Israeli war against Iran.

By Olivia Le Poidevin and Emma Farge

GENEVA, March 17 (Reuters) - Medical supplies to clinics dealing with the humanitarian crisis in Sudan could run out within two weeks unless shipments are rapidly rerouted after disruptions due to the conflict in the Middle East, the charity Save the Children said.

The expanding U.S.-Israeli war on Iran has shaken global supply chains, with airspace closures and the halt of shipping ​through the Strait of Hormuz.

Some $600,000 worth of essential medicines are stuck in ports in Dubai, the charity said.

By Andrew Gray

BRUSSELS, March 17 (Reuters) - European Union foreign policy chief Kaja Kallas called on the United States and Israel on Tuesday to end their war with Iran and said the EU was consulting with governments in the Middle East about how to bring the conflict to a conclusion.

In an interview with Reuters in Brussels, Kallas also said the door was not closed to European participation in efforts to restore freedom of navigation in the Strait of Hormuz but it would be most likely to come as part of a diplomatic solution.

March 17 (Reuters) - Tensions between Pakistan and Afghanistan flared this week after the Afghan Taliban government accused its neighbour of attacking a drug rehabilitation centre and killing more than 400 people - a charge denied by Islamabad.

Amid fears of a sharp escalation in the conflict, here is a look at how the militaries of the allies-turned-foes compare, according to data from the London-based International Institute for Strategic Studies.

OVERVIEW

By Emma Farge

GENEVA, March 17 (Reuters) - Tens of millions more people will face acute hunger if the Iran war continues through to June, according to analysis from the World Food Programme released on Tuesday.

The U.S.-Israeli attacks on Iran that began on February 26 have choked up key humanitarian aid routes, delaying life-saving shipments to some of the world's worst crises.

An extra 45 million people could face acute hunger if the Middle East war rages on beyond June, swelling the number worldwide to a "terrible" high, the United Nations warned Tuesday.

The war, now in its third week, and its shockwaves on food and fuel costs could price families out of staple foods far beyond the region, the UN's World Food Programme said.

"The escalating humanitarian fallout from the conflict in the Middle East is growing more concerning by the day," warned WFP deputy executive director Carl Skau.