Hundreds of thousands of protesters are mobilizing against the French president's plan to legalize gay marriage, streaming into Paris by bus, car and specially reserved high-speed train.

Police are expecting about 300,000 people to march toward the Eiffel Tower from three different points in the city, tying up traffic and closing subway stations for hours in what could be the largest demonstration in a decade.

President Francois Hollande has promised to legalize gay marriage, allowing same-sex couples legal protections that would allow them to adopt, among other things.

The proposal has grown increasingly unpopular in France, led by opposition from religious leaders. About 50 percent of French favor legalizing gay marriage, down from as high as 65 percent in August.