LONDON — Britain was forced to abort a second airdrop of humanitarian aid to refugees in northern Iraq on Monday over fears about hitting the people below, a military spokesman said.

Another attempt to deliver desperately needed food and water to Yazidis who fled Islamic State jihadists and are stranded on Mount Sinjar is likely to take place within the next 24 hours.

“The ongoing effort to get badly-needed supplies to displaced people in northern Iraq continues,” a spokesman for the Royal Air Force (RAF) said.

“The safety of the Yazidi community is paramount. With a number of people at the drop sites this morning, the crew made the responsible decision not to carry out the air drop to ensure that the lives of those in the area would not be put at risk,” the spokesman said. “We plan to deliver the next drop as soon as possible.”

Two transport planes left Britain on Saturday and the first drop was made that night, including 1,200 water containers providing 6,000 liters of water, and 240 solar lanterns that double as phone chargers.

Britain is also working with the United States, Iraq’s autonomous Kurdistan region, Turkey and other international partners on how to bring the Yazidis down from the mountain, officials say.

On Monday, the United States began urgently shipping arms and ammunition to the Iraqi Kurdish forces battling an advance by extremist Islamic State militants, a State Department spokeswoman said.

“We’re working with the government of Iraq to increasingly and very quickly get urgently needed arms to the Kurds,” Marie Harf told CNN.

“This includes the Iraqis providing their own weapons from their own stocks, and we’re working to do the same thing from our stocks of weapons that we have.”

Britain has offered surveillance and refueling support for US aid flights, but insists it will not be joining Washington in conducting air strikes on the IS militants.

A spokeswoman for Prime Minister David Cameron’s office reiterated his position on Monday, and said that a recall of parliament from its summer recess to discuss Britain’s response was “not on the cards.”

“We have been clear that British combat troops will not be going back to fight in Iraq,” she said. “There is not a discussion under way on the UK playing a role in air strikes.”

Asked about the possibility of arming local forces on the ground, she said: “We do think it’s important that the Iraqi forces, including the Kurdish forces, are able to respond to IS and to tackle this crisis in the country.

“We will look at what options there are that might enable them to do that. But there have not been substantive discussions on that yet and there are certainly no decisions.”