Three US paper companies and the United Steelworkers have filed an antidumping case against China and Indonesia as the union fulfills its promise to protect American industries, the Wall Street Journal reported. The petitioning parties said the timing of their filing on the eve of the G20 economic summit in Pittsburgh was coincidental but the move threatens to further escalate tensions between the US and China, following President Barack Obama recent decision to endorse high tariffs on Chinese tire imports. The latest petition – which states that China and Indonesia have been dumping tons of shiny, coated paper in the US at below cost price – doesn’t require Obama’s approval as it is using a different legal route to the tire tariffs case. Speaking to Obama on the sidelines of a UN summit, President Hu Jintao said US tariffs were "not in the interests of both countries and similar cases should not happen again," state media reported.