A big new bridge linking China and North Korea opened on Thursday, 12 years after its completion, deepening economic ties between the Asian giant and its isolated nuclear-armed neighbor.

China is North Korea’s largest trading partner and a vital source of diplomatic, economic and political support for the reclusive nuclear state, although ties have not always been smooth.

Hundreds of people gathered on Thursday on the Chinese side for the opening of the 3,026-meter New Yalu River Bridge.