French President Emmanuel Macron called for another overhaul of the global taxation system to finance the fight against poverty and climate change, building on recent efforts for a minimum levy on corporations.

The new taxation could hit airline tickets, financial transactions or shipping, Macron said at an international summit in Paris on reforming the global financial system. For it to be successful, countries would have to work together to avoid businesses relocating activity to avoid national levies, he said.

“A century ago we said socialism in one country doesn’t work — well, international tax in one country doesn’t work either,” the president said on France Info radio.

Macron said negotiations could be finalized at the Organization for Economic Cooperation and Development, which has hosted talks between around 140 countries on international taxation rules.

However, it’s not clear those talks could provide a blueprint for an international climate tax. That’s partly because those negotiations dragged on for years, and the part of the two-pillar deal that would affect how big tech firms are taxed is still not finalized.

The rules on an effective 15% minimum tax are further advanced, but the potential additional revenues from that system go directly to national treasuries, rather than being pooled internationally for a particular type of spending.

Macron said there could also be talks at the International Maritime Organization on a tax on shipping.

“The maritime transport sector is not taxed at all,” Macron said. “It has to be taxed, but not just French companies - the French, the Northern Europeans and the Chinese need to be taxed.”