Johnson attended a world leaders' summit that kicked off the United Nations climate conference in Glasgow last week, and will return to the Scottish city Wednesday.

So far the conference has produced headline-grabbing announcements in areas including ending coal power, funding green technology and reversing deforestation. But the almost 200 nations attending remain far from sealing a deal that could limit global warming to the internationally agreed goal of 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.

Johnson's office says issues still being hammered out include ''a common time frame for national commitments on emissions reductions and agreed methodology for countries to report on their climate action'' -- mechanisms that can be used to hold countries to their commitments.

There is also an unkept promise from rich nations to give more money to the countries most vulnerable to climate change -- often developing nations that have done least to cause it.

Johnson, along with UN Secretary General Antonio Guterres, will meet with government officials, negotiators and civil society groups in an attempt to inject momentum into the talks.

Johnson said climate change ''is bigger than any one country and it is time for nations to put aside differences and come together for our planet and our people. We need to pull out all the stops if we're going to keep 1.5C within our grasp.'' COP26 is due to end Friday, though the talks could stretch on longer.