Agreement is "within reach but not yet achieved", the French Foreign Affairs Minister said on Saturday, while predicting that compromises were needed to reach a legally binding, lasting and fair deal.
On the same day President François Hollande met representatives of 14 NGOs to discuss their proposals for an "ambitious, universal and equitable agreement" to avert global warming disaster.
But 24 activists were placed under house arrest to stop them defying a ban on marches and protesters were prevented from entering a "senstive" area near Paris on Saturday.
Activists nevertheless planned to form a human chain in the east of Paris and to place a pile of shoes, representing people who would have joined the demonstration had it taken place, in the Place de la République.
One pair of shoes is marked with the name of Pope Francis and the number of the encyclical in which he denounced the threat of global warming.
Some 40,000 people, including 10,000 delegates from 195 countries, journalists, scientists and visitors, were expected at the Le Bourget conference centre.
They were to be protected by 2,800 police at the site and 6,300 in Paris itself.