The Paris climate talks entered stage of substantive negotiations on Tuesday as negotiators began to turn political will that their leaders expressed into concrete solutions to various disputes over a new climate agreement.

Officials from 195 countries have one final week to slim the agreement draft which now runs over 50 pages to a manageable level so that their ministers could read when they join the table next week.

Starting on Monday evening, immediately after some 150 world leaders left the conference center after showing unity in fighting the common challenge of climate change, negotiators dived into sticky issues that have to be resolved over the next two weeks.

"Everybody works hard, day and night," said China's chief negotiator Su Wei. "Leaders have injected a strong impetus into negotiations. It is negotiators' job now to discuss the agreement text word by word, line by line."

Draft of the Paris agreement was shown on screens for negotiators to scrutinize. Bilateral and multilateral discussions among delegates from different countries were also underway.

The final draft was expected to be hammered out on Saturday. Based on that, ministers will make decisions on sensitive political issues.

Finance, emission reduction targets, long-term goal, reviewing mechanism are among various conflicts that negotiators have to settle.

"The challenge is how to translate that willingness (to be united in addressing climate change) into concrete solutions to the difficult areas of the negotiation. That's what we are going to do during the next days," said Brazilian chief negotiator Antonio Marcondes.

He warned against developed countries' attempt to amend the United Nations Framework Convention on Climate Change, which obliges developed countries to take lead in cutting emissions and to provide finance and technology support to developing countries.

"We are negotiating this Paris agreement under the Convention, so the Convention is there to be maintained, preserved and not amended," he said.

In 2009, developed countries promised to provide 100 billion U.S. dollars per year by 2020 to help developing countries reduce emissions and adapt to climate change. According to calculations of World Resources Institute, however, only 17 billion U.S. dollars were provided in 2012.

Developing countries want developed countries to offer a clear path towards reaching the 100-billion-U.S.-dollar target and to scale up support from that level after 2020 when the Paris agreement comes into force.

"It's a fundamental part of a successful Paris agreement," Marcondes said. "We are very much expecting that the developed countries will live up to their responsibilities derived from the Convention." Endit