The IMO's lobbying to give seafarers key worker status is ramping up ahead of a meeting of world leaders at the UN General Assembly session that begins on Tuesday in New York.

Shipping's global regulator has joined seven other UN agencies to demand authorities take immediate action on facilitating crew changes as hundreds of thousands of seafarers languish on board their ships, some for a year or longer.

"It is because of the sacrifices of seafarers who have continued working after their contracts have expired, that ports have remained open for trade, so allowing cargo operations to be carried out in a timely manner and goods to continue to circulate smoothly," the joint statement to all world governments read.