to discuss, not least for their ongoing disputes over trade, technology, taiwan, and fentanyl. the bbc s james clayton is in san francisco and he s filed this report with the latest. apec has started here and it is a huge moment for the city of san francisco, the biggest summit to be held here since the united nations charter was signed here in 1916. this is a huge economic summit. you are talking about more than 50% of all of the world s trade belongs to the 21 nations who will be attending here this week. and we are talking about 40% of the world s population. so it is a big economic conference, but by far the biggest ticket item here is the meeting between president biden and his counterpart in china, xijinping. relations between those two nations have not been good as late. they last met last year in indonesia and since then you have had that moment where the american government shot down the chinese spy balloon and flaming tensions in the south china sea and also joe bid