Kerry, who is the US’s first ever Special Presidential Envoy for Climate, will be attending the climate summit along with President Joe Biden, and other world leaders.
He told the BBC that he wanted COP26 to help raise the ambition of the world’s major economies, and described the summit as the "greatest test of global citizenship".
Kerry said: "Glasgow is coming at a point where these scientists have told us we have about nine years remaining within which to make the most critical decisions. Those decisions have got to really start in earnest and in a significant sum in Glasgow."
"We have to get on the road here and we've been talking about it for 30 years".
"So this is really what Glasgow is about, the last best hope to do what the scientists tell us we must which is to avoid the worst consequences of climate by making decisions now and implementing them now."
Kerry, who previously served as Secretary of State from 2013 to 2017, was appointed to Biden’s administration in November 2020. He has promised to make up for what he describes as the “reckless behaviour” of ex-president Donald Trump, who pulled the US out of the Paris Climate Accords, and has said that America will now move forward with climate negotiations with “humility and ambition".