The US sees decarbonising the shipping industry as a top priority for combating climate change and is willing to go a step further than the International Maritime Organization.

The US president's special climate envoy, John Kerry, said on Tuesday that Washington would focus on helping the global fleet hit net zero emissions in 30 years time.

As it stands, the IMO intends to cut emissions by 50% by 2050 against a 2008 baseline.

"The technology we need to decarbonise shipping is known to us.