Half-way through talks to breathe life into the Paris climate deal negotiators haggle over how to share the cost of curbing global warming and struggle to bridge deep political divides.

The US State Department has officially informed the United Nations it will withdraw from the Paris Climate Agreement in a document issued on Friday, but left the door open to re-engaging if the terms improved for the United States.

Climate change is undeniable and it is "absolutely essential" the world fight the problem together, United Nations Secretary-General Antonio Guterres argues, as US President Donald Trump considers pulling out of the Paris climate deal.