No Trump! the rally of hundreds shouted, growing louder as it neared the United States embassy in the center of South Korea's capital Seoul.

A line of police buses stopped them from reaching the gates, but a stage and loudspeaker ensured their voices soared above Gwanghwamun square and within earshot of US President Donald Trump's representatives.

This was a small rally by the standards of South Korea's vibrant protest culture. And it wasn't the only one under way. A few hundred meters to the north, at the gates of Gyeongbokgung palace, marchers held aloft more banners as they chanted a very different message.

No China, along with a smattering of CCP [Chinese Communist Party] out! The numbers weren't huge, but this footfall through central Seoul on a sunny Saturday indicated the diplomatic dance South Korea's President Lee Jae Myung will have to perform as he hosts leaders from both the US and China.

Seoul is a key US ally, a friendship forged in blood during the Korean War, yet it also relies heavily on China, its largest trading partner.

It's a particularly fraught moment - South Korea finds itself caught between a rock and a hard place, says Darcie Draudt-Vejares from the Carnegie Endowment for International Peace.

Lee is hosting talks between Trump and Xi Jinping that may yield a breakthrough in their trade war.

Negotiations earlier had seemed promising, with Seoul agreeing to invest $350 billion in the US and buy $100 billion worth of liquefied natural gas in exchange for lower tariffs, but recent tensions from immigration raids have strained ties.

The South Korean public largely views the US positively, yet sentiments against China have surged due to various historical grievances and contemporary economic aggression.

As protests rise and diplomatic stakes become clearer, South Korea is navigating a critical week in its relationship with both nations, balancing economic needs against public sentiment.