World leaders have arrived in the German city of Hamburg for the two-day G20 summit which formally starts on Friday. 

German Chancellor Angela Merkel will be hosting the summit, saying participants would address regulating financial markets, fighting terrorism and pandemics, and combating climate change.

When it comes to the Paris Agreement, she said: "We are still negotiating, there are various options we can discuss, we know the US has withdrawn from the Paris Agreement, all others or at least as far as I know, many many others are still committed to the Paris Agreement."

"And how that turns out is something we will tell you at the end. When we have finish the communique," she added.

Chinese President Xi Jinping will also meet with US President Donald Trump. Xi said there could be no final G20 communique on the climate issue without the United States being a signatory.