When George Bush senior visited Seoul as US president 20 years ago, things were simple – the US was the undisputed main ally and trade partner. There was only one weekly flight from South Korea to China, the communist foe.

Barack Obama, US president, yesterday arrived in a South Korea where the US is no longer the only show in town. China is now the main trade partner, with 642 flights each week. While the US is still the chief political ally, Mr Obama's cheery soundbites on Korean issues are not convincing Seoul that Washington is dedicating enough thought to the peninsula.

On the military front, ties remain robust, with the US committed to its South Korean presence. But vital issues such as a trade agreement and North Korea's nuclear weapons have been sidelined in the US, while China plays a greater role in both Koreas.