Oh, they'd be happy to get on board if the other countries (cough US) would just pay for it. Why do think the US keeps dropping out of these kinds of talks? It's because they keep trying to make the US their main income completely out of proportion. "Every country needs to do this but let's have the US pay for 60%-70% of the total world contribution." The US as a country has already spent insane amounts of money to "help" other countries clean up instead of spending that money to help clean up the US.
All but 2 of the 10 highest polluting rivers (plastic waste) are in Asia with 6 of those being in China so in reality it's China continually pumping plastic waste into the world's oceans.
The yangtze river (China) the single highest polluter of the list with 1.8million metric tons of waste, more than all others combined.