The US has urged governments to act to prevent a "humanitarian catastrophe of epic proportions", amid fears Iraq's Mosul dam could collapse.

Concern has been growing in recent months over a possible breach in the country's largest dam.

This would unleash a wave as high as 14 metres (45ft), devastating Mosul and flooding much of Baghdad, with up to 1.5 million people at grave risk.

US Ambassador Samantha Power has called on UN member states to take immediate action.

Speaking after hosting a meeting with Iraq's UN Ambassador Mohamed Ali Alhakim, she said: "It is crucial that all UN member states quickly get informed about the magnitude of the problem and the importance of readiness to prevent a humanitarian catastrophe of epic proportions."

The ambassador described briefings she had received from technical experts, engineers and representatives from UN aid and development agencies as "chilling".

The dam in northern Iraq was built on an unstable foundation that continuously erodes.

The already flawed structure was weakened further when maintenance could not be carried out because of the Islamic State takeover of the facility in 2014.

"In the event of a breach, there is the potential in some places for a flood wave up to 14 metres high that could sweep up everything in its path, including people, cars, unexploded ordnance, waste and other hazardous material, further endangering massive population centres that lie in the flood path," Ms Power said in a statement released by the US mission.

She said repair work must be carried out as soon as possible, and Iraqis must be told about the best evacuation routes.

Approximately 500,000 to 1.47 million Iraqis live in the flood path, the US statement said.

Italian company Trevi has been chosen to carry out crucial repair work on the dam, which is currently protected by Kurdish Peshmerga troops.

The contract is worth 273m (192m) and will reinforce and maintain the dam for 18 months.

Italy plans to send 450 troops to protect the site, which is 2.2 miles (3.6km) long and close to territory held by IS.

Militants from the group seized the dam in August 2014, raising fears they might blow it up.

It was retaken two weeks later by Iraqi government forces supported by US-led coalition airstrikes.

Mosul Dam 'Humanitarian Catastrophe' Warning